Clinical Oncology xxx (2016) 1e7 Contents lists available at ScienceDirect
Clinical Oncology journal homepage: www.clinicaloncologyonline.net
Original Article
Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK F. Abolaban *y, S. Zaman y, J. Cashmore z, A. Nisbet yx, C.H. Clark x{ * Nuclear
Engineering Department, King Abdulaziz University, Jeddah, Saudi Arabia Department of Physics, University of Surrey, Guildford, UK z Hall-Edwards Radiotherapy Research Group, University Hospital Birmingham, Birmingham, UK x Department of Medical Physics, Royal Surrey County Hospital, Guildford, UK { National Physical Laboratory, Teddington, UK y
Received 18 September 2015; received in revised form 8 December 2015; accepted 5 January 2016
Abstract Aims: Between 2012 and 2014 the number of patients treated in the UK with intensity-modulated radiotherapy (IMRT) techniques increased significantly. One reason for this was the radiotherapy innovation fund for the centres in England. Before the announcement of the fund, a survey of radiotherapy centres was carried out in 2012 which collected data on IMRT uptake, obstacles to implementation, equipment used, delivery techniques and verification methods. A repeat survey was carried out in 2014 to identify key changes to IMRT quality assurance and verification practices. Materials and methods: An online questionnaire was sent out to all 65 UK radiotherapy centres in the summer of 2012 and again in the summer of 2014. Questions covered background and equipment, machine tolerance and quality assurance, machine-based verification, software-based verification and future plans. Results: There have been significant changes in the delivery techniques used for IMRT, with more than twice as many centres reporting the use of volumetricmodulated arc therapy techniques in 2014 compared with 2012. This has been combined with an increase in Monte Carlo-based algorithms in treatment planning systems. In 2012 all centres reported the need to carry out machine-based measurements for IMRT plan verification, dropping to 93% in 2014. Nineteen per cent of centres now report making only one measurement per month for prostate plans and 8% of breast plans never have physical measurements. Most centres use detector arrays for quality assurance measurement (86% in 2012 and 91% in 2014), but a significant number still use film and/or ionisation chambers (51% and 41%). In the analysis of these measurements there has been an increase in the use of tighter criteria. There has been a significant increase in the use of software for verification from 63% in 2012 to 95% in 2014. All centres reported that they needed further resources in order to efficiently achieve the quality assurance required for the number of patients planned to be treated in their centre. Conclusions: The increased numbers of patients being treated with IMRT has meant that there have been significant changes in the way that quality assurance is carried out. These have been mainly in the reduction of measurements and the increase in software-based verification. However, quality assurance is still a significant burden and still has an effect on the numbers of patients who can be treated with IMRT. Crown Copyright Ó 2016 Published by Elsevier Ltd on behalf of The Royal College of Radiologists. All rights reserved.
Key words: IMRT; quality assurance; VMAT
Introduction The uptake of intensity-modulated radiotherapy (IMRT) techniques within the UK was relatively slow compared with some other countries and in August 2012 only 13.6% of radiotherapy patients in England received IMRT [1e3]. Later
Author for correspondence: C. Clark, Department of Medical Physics, Royal Surrey County Hospital, Edgerton Rd, Guildford, Surrey GU2 7XX, UK. E-mail address: [email protected] (C.H. Clark).
that year the Department of Health England created a Radiotherapy Innovation Fund, releasing £23million of funding to cancer centres to increase IMRT capacity. The aim of the fund was to address obstacles to IMRT treatment and to reach a goal of treating more than 24% of all radical radiotherapy patients with IMRT, with this figure already reaching 22.3% by April 2013. It has been suggested that up to 50% of radiotherapy patients may benefit from IMRT [4e6]. Volumetric-modulated arc therapy (VMAT) has now also been introduced to reduce the time taken to deliver IMRT and has been implemented more quickly than static
http://dx.doi.org/10.1016/j.clon.2016.01.013 0936-6555/Crown Copyright Ó 2016 Published by Elsevier Ltd on behalf of The Royal College of Radiologists. All rights reserved.
Please cite this article in press as: Abolaban F, et al., Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK, Clinical Oncology (2016), http://dx.doi.org/10.1016/j.clon.2016.01.013
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F. Abolaban et al. / Clinical Oncology xxx (2016) 1e7
gantry IMRT was, with over 50% of UK centres now offering this [7]. Thirty-eight per cent of the fund was spent on advanced treatment planning, 22% on linac upgrades, 17% on imageguided radiotherapy equipment and 12% on IMRT and image-guided radiotherapy quality assurance. The remaining (11%) was spent on staffing costs, training, software and immobilisation equipment [8]. The quality assurance burden associated with the implementation of IMRT and VMAT has been considerable and the desire to increase patient numbers means that verification processes play a key role in the extent to which a centre can provide this service [9]. This burden generally falls to the physics department to address. Before the announcement of the fund a survey of radiotherapy centres was carried out in 2012 which collected data on IMRT uptake, obstacles to implementation, equipment used, delivery techniques and verification methods. A repeat survey was carried out in 2014 to identify key changes to IMRT quality assurance and verification practices. Such information may inform centres seeking to increase their IMRT provision further, of potential areas to address and resources required.
Materials and Methods An online questionnaire was sent out at two different time points, July to October 2012 and July to October 2014, to all 65 UK radiotherapy centres. For the purposes of this survey, IMRT was defined to be inverse planned and included all linac-based deliveries (including TomoTherapy and CyberKnife) as well as static and rotating gantry techniques. Questions covered background and equipment, machine tolerance and quality assurance, machine-based verification, software-based verification and future plans.
Results In 2012 and 2014, 96.9% (63/65) and 89.2% (58/65) of centres responded, respectively. A large range of experience was reported from >10 years to only just started. How the Radiotherapy Innovation Fund was used For the English centres, the top three answers for how the Radiotherapy Innovation Fund was spent were treatment planning system (TPS) software (licenses) 88.9%, TPS hardware (51.1%) and delivery hardware (linacs) 44.4%. However, when asked how a further fund would be spent, TPS licences was still the top response (71.4%), second was increasing the number of staff members (57.1%) and on TPS hardware (49.0%) was the third most common answer. Equipment The proportions of centres using linacs from each manufacturer were consistent at the two time points 2012 (2014), being 66% (68% in 2014) Varian (Varian Medical
Systems Inc., Palo Alto, CA, USA), 27% (31%) Elekta (Elekta AB, Stockholm, Sweden), 4% (4%) Siemens (Siemens AG, Erlangen, Germany), 11% (9%) TomoTherapy (AccurayTomo-Therapy, Madison, WI, USA) and 9% (9%) CyberKnife (Accuray-Tomo-Therapy). It should be noted that a number of centres used more than one manufacturer. In 2014 all centres used 6 MV with some use of 10 MV (30% up from 22% in 2012) and a few using 8 MV (3%, same as 2012) and 15 MV (3%, increased from 2% in 2012). There was a shift towards more complex treatment planning algorithms, with an increase in Monte Carlo-based algorithms (from 7.0% to 17.6%) and a reduction in pencil beam methods (23.9% to 14.9%). There was also a significant change in delivery techniques with 74% of centres reporting the use of VMAT techniques (compared with 34% in 2012). There was also a slight reduction in static field IMRT (41% to 35% for dynamic [Varian and CyberKnife] and 49% to 41% for step and shoot) (see Figure 1). Numbers Treated In 2012, 82% of centres reported a limit on the numbers of IMRT patients they were able to treat. This was reported to have dropped to 48% in 2014. Typical reasons given for this were limited resources (TPS and staff), clinician outlining time, machine availability and, of course, the availability of funding for these resources. Timing The survey also asked how long it took to carry out planning and quality assurance for different treatment sites (see Tables 1 and 2). In Figure 2 the total amount of time for head and neck cases shows that overall there was a decrease in the time taken for planning and quality assurance, with a marked decrease in those taking 4þ h and an increase in 1e3 h. Audit There are now a considerable number of external audits available with an IMRT component and 87% of centres have been credentialed to join one of several trials with IMRT in the National Cancer Research Institute portfolio in 2014. Seventy-six per cent took part in the national IMRT audit [10] and 60% in the national rotational IMRT audit [7,11]. More recently there has been an increase in the number of centres participating in interdepartmental audits with IMRT measurements (from 45% in 2012 to 62% in 2014) [12]. Machine Tolerance and Quality Assurance Fifty-five radiotherapy centres responded to the questions about their Multi-leaf collimator (MLC) tests, tolerances and frequencies. The most common test and frequencies with tolerances are given in Table 3. In both 2012 and 2014, about 40% of radiotherapy centres used in-house developed tests for MLC tests, including leaf speed, leaf calibration, dosimetric leaf gap, picket fence test, log files, complex fluences and electronic portal imaging
Please cite this article in press as: Abolaban F, et al., Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK, Clinical Oncology (2016), http://dx.doi.org/10.1016/j.clon.2016.01.013
F. Abolaban et al. / Clinical Oncology xxx (2016) 1e7
3
Which delivery methods do you use for IMRT delivery for Linac based 2012 treatment?
Percentage of response
2014 80% 70% 60% 50% 40% 30% 20% 10% 0%
Fig 1. The proportion of different techniques used for intensity-modulated radiotherapy (IMRT) delivery in 2012 and 2014.
device (EPID)-based field position checks. Whether undertaking published or in-house MLC tests, 56% of centres reported spending less than 1 h doing these measurements. Per Patient Quality Assurance: Measurement In 2012 all centres reported the need to carry out machine-based measurements for IMRT plan verification
for each patient, dropping to 93% in 2014, with four centres stating that they do not do any measurements to check IMRT plans. Overall, measurements-based IMRT quality assurance was most common in head and neck (84%) and lung Stereotactic Ablative Body Radiotherapy (SABR) (82%). However, 19% of centres reported making only one measurement per month for prostate plans and 8% of centres reported breast plans never having physical measurements.
Table 1 Length of time in 2014 taken to plan (excluding contouring and checking) intensity-modulated radiotherapy patients (most frequent answer shown in bold)
Head and neck Prostate Prostate and pelvic nodes Breast Lung Lung SABR Gynaecological Other
1e2 h
2e3 h
3e4 h
4e5 h
1 day
1þ day
Variable
8.2% 68.8% 29.5% 41.7% 33.3% 17.6% 28.9% 20.0%
24.5% 14.6% 22.7% 8.3% 12.5% 11.8% 36.8% 22.9%
16.3% 10.4% 29.5% 16.7% 41.7% 17.6% 15.8% 20.0%
20.4% 4.2% 2.3% 8.3% 4.2% 17.6% 10.5% 8.6%
18.4% 2.1% 11.4% 12.5% 0.0% 23.5% 2.6% 2.9%
8.2% 0.0% 4.5% 4.2% 4.2% 11.8% 2.6% 5.7%
4.1% 0.0% 0.0% 8.3% 4.2% 0.0% 2.6% 20.0%
SABR, Stereotactic Ablative Body Radiotherapy. Table 2 Length of time taken in 2014 to carry out quality assurance for intensity-modulated radiotherapy patients (most frequent answer shown in bold)
Head and neck Prostate Prostate and pelvic nodes Breast Lung Lung SABR Gynaecological Other
0e30 min
30e60 min
1e2 h
2e3 h
3e4 h
4e5 h
5þ h
45.8% 59.6% 48.8% 56.0% 50.0% 22.2% 48.6% 35.3%
35.4% 27.7% 34.9% 32.0% 37.5% 38.9% 37.8% 47.1%
10.4% 10.6% 14.0% 8.0% 12.5% 27.8% 10.8% 14.7%
2.1% 0.0% 0.0% 0.0% 0.0% 11.1% 0.0% 2.9%
2.1% 2.1% 0.0% 0.0% 0.0% 0.0% 2.7% 0.0%
2.1% 0.0% 2.3% 4.0% 0.0% 0.0% 0.0% 0.0%
2.1% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
SABR, Stereotactic Ablative Body Radiotherapy. Please cite this article in press as: Abolaban F, et al., Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK, Clinical Oncology (2016), http://dx.doi.org/10.1016/j.clon.2016.01.013
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F. Abolaban et al. / Clinical Oncology xxx (2016) 1e7
Table 3 Most common MLC tests with frequency and tolerances in 2014 Test
Frequency
Tolerance
Sweeping gap MLC auto recalibration Log file analysis Size of light field Picket fence test Static and dynamic MLC checks VMAT MLC speed test MLC field shape definition Dynamic leaf gap with gantry rotation
Daily Daily Daily Weekly Monthly Monthly Monthly Monthly Monthly
2%
VMAT, volumetric-modulated collimator.
arc
therapy;
MLC,
2 mm 1 mm 1e2 mm 2% e0.3 mm Multi-leaf
Most lung SABR techniques were measured for every patient, but 6% reported having dropped this to one in five or to one per month. Most centres used detector arrays (86% in 2012 and 91% in 2014) or EPID (24% and 26%) for dose distribution measurements. However, a significant number still used film and/or ionisation chambers (51% and 41%). A few centres (5% in 2014) started to use MLC movement log files (dynalog files) for verification of delivery. The most commonly used gamma parameters to analyse the measurements was 3%/3 mm, but for the more complex plans (head and neck, prostate and pelvic node) there was an increase in the use of 3%/2 mm (12% to 20%) and 2%/ 2 mm (0% to 10%) (see Figure 3). In 2012 the split between local and global gamma was 34.8% and 69.8%, respectively (some use both), whereas in 2014 there was a reduction in the use of global gamma to 55.2%. In both surveys there was a range of normalisation points used, with the most common being maximum dose 31.1% in 2012 (15.6% in 2014),
user chosen 24.4% (37.8%) and no normalisation 28.9% (33.3%). The use of global/local evaluation and normalisation methods were mainly influenced by the functionality of the software. In order to define the appropriate tolerances to use, 77.1% (up from 64.3% in 2012) used an in-house data review, 62.5% (50%) consulted the literature, 35.4% (12.5%) used the IPEM report 96 [9] and 4.2% (1.8%) used the same as for their conformal techniques. In 2012, 94% of quality assurance measurements were made by physicists, with the remaining being by technicians or engineers. By 2014 this had changed to 88% by physicists and 6% by radiographers, with the remaining again by technicians or engineers. However, the checking of quality assurance measurements was consistently carried out by physicists. In 2014, 80% of the radiotherapy centres reported that the most common reason for out of tolerance measurements was the plan being too highly modulated. The next most common reasons were that the point dose measured was in a gradient (41%) or that the phantom was not correctly set up (39%); 36.2% never changed a plan based on the results of quality assurance measurements. The final question in the measurement-based quality assurance section was how frequently quality assurance was carried out for each site (see Figure 4 for data from 2014). Prostate treatment was the site where centres had most commonly cut down from measuring every patient. Breast was the most common site where measurements are no longer made. Per Patient Quality Assurance: Calculation There was a significant increase in the use of software for verification from 63% in 2012 to 95% in 2014, with a
Approximately how long does it take to plan (excluding contouring and checking) and do QA for your IMRT Head and neck paƟents?
number of responding centres
14
2012
12
2014
10 8 6 4 2 0 1 - 2 hrs
2 - 3 hrs
3 - 4 hrs
4 - 5 hrs
1 day
1+ day
Variable
Fig 2. Time taken to plan and carry out quality assurance for head and neck intensity-modulated radiotherapy (IMRT). Please cite this article in press as: Abolaban F, et al., Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK, Clinical Oncology (2016), http://dx.doi.org/10.1016/j.clon.2016.01.013
F. Abolaban et al. / Clinical Oncology xxx (2016) 1e7
2014 these were 25%, 12.5% and 37.5%, respectively. Fortytwo per cent of centres cited that they wished to introduce EPID-based quality assurance, introduce more software-based verification (48%) or stop measurements altogether (25%).
Percenatge of respondants
Prostate 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0
2012
Gamma index criteria
Prostate and Pelvic Nodes Percentage of respondants
Discussion
2014
2%/2mm 3%/2mm 3%/3mm 4%/3mm 4%/4mm 5%/5mm
80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0
2012 2014
2%/2mm 3%/2mm 3%/3mm 4%/3mm 4%/4mm 5%/5mm
Gamma index criteria
Head and Neck Percentage of respondants
5
90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0
2012 2014
2%/2mm 3%/2mm 3%/3mm 4%/3mm 4%/4mm 5%/5mm
Gamma index criteria
Fig 3. The gamma index criteria used for the three most common sites, shown in 2012 and 2014.
simultaneous increase of second dose distribution calculations from 9% to 26%. These were predominantly calculated by physicists (74%), but the remainder were carried out by other staff groups (17% dosimetrists, 3% radiographer and 6% other). In contrast with the measurement-based checks being all checked by physicists, 7% of these software calculations are now signed off by dosimetrists. Changes in Quality Assurance Processes In 2012, when asked what changes they wanted to make to their quality assurance process, the most frequent answers were a change in who does the quality assurance (37.8%), a change to a different type of measurement (51.1%) and a reduction in the number of measurements (57.8%). In
The increase in IMRT has been accompanied by a significant increase in the use of VMAT, which increases delivery speed, enabling centres to maintain patient throughput on their linacs. This has in turn meant that more patients can benefit from an IMRT-based treatment, and many centres are now able to deliver IMRT to as many patients as required by their clinical case mix [13]. However, there is still a wide variation in access rate by centre, with four centres not achieving the 24% target by February 2014 and five centres exceeding 40% [6]. This increase has also had an effect on the way quality assurance is carried out and it has been shown that most centres have reviewed their quality assurance approaches in order to absorb this increase. An increase in experience and confidence has also allowed a change in the way quality assurance is undertaken. Overall there has been a reduction in the time needed to plan and quality assurance, which has also been aided by the upgrades in the TPSs, which have included implementation of more advanced algorithms as well as increased computing power. The increase in experience and confidence in local quality assurance results has also led to an increase in inhouse review of gamma tolerances. Overall these have been tightened and there is a move away from the original 3%/3 mm towards a tighter distance to agreement value of 2 mm. This may mean that delivery is becoming more accurate with smoother VMAT deliveries or could also be due to greater experience in planning and quality assurance. However, the developments in the quality assurance tools such as the detector arrays, have also increased the passing rates, due to better resolution and interpolation methods between the measurement points. The burden of patient-specific quality assurance is still considerable for the physics staff groups, but there is now some sharing with other staff groups and streamlining of the timing of quality assurance into the working day. Methods such as EPID dosimetry shorten the set-up time for quality assurance equipment, allowing a quicker measurement to be made, often accompanied by offline analysis by different staff groups at a later time. There has been a significant increase in software-based verification, allowing both point doses and, in some cases, dose distributions to be analysed without need of the linac. This is expected as it is in line with international recommendations [14,15]. The tumour sites where this is most commonly seen (breast and prostate) are generally more straightforward to plan and hence a reduction in measurement as experience increases is appropriate and all centres should consider this move once they have sufficient experience. The move towards calculation-based
Please cite this article in press as: Abolaban F, et al., Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK, Clinical Oncology (2016), http://dx.doi.org/10.1016/j.clon.2016.01.013
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F. Abolaban et al. / Clinical Oncology xxx (2016) 1e7
Fig 4. Frequency of performing machine-based quality assurance, by site, in 2014.
verification also indicates a trend towards a wider staff base and responsibility.
Conclusions Improved resources have increased the numbers of patients being treated with IMRT, but a further increase in both staff numbers and TPS hardware and software is cited as required for a further increase in capacity. There have been significant changes in the way that quality assurance is carried out. These have been mainly in a reduction in measurements and an increase in software-based verification. This has been aided in English centres by the Radiotherapy Innovation Fund, but quality assurance is still a significant burden and still has an effect on the numbers of patients who can be treated with IMRT.
Acknowledgements This work was supported by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under grant no. (D1435-605-135). The authors therefore gratefully acknowledge the DSR technical and financial support. The authors would like to thank the medical physicists in the following hospitals for taking the time to complete the survey: Aberdeen Royal Infirmary, Addenbrooke’s, Arden Cancer Centre, Beatson West of Scotland Cancer Centre, Bristol Haematology and Oncology Centre, Churchill Hospital, University Hospital Birmingham, Cheltenham Hospital, Clatterbridge Cancer Centre, Colchester Hospital, Derriford Hospital, Edinburgh Cancer Centre, Guy’s & St Thomas, Imperial College, Ipswich Hospital, James Cook University Hospital, Kent Oncology Centre, Lincoln Oncology Centre, Mount Vernon Cancer Centre, Ninewells Hospital, Norfolk & Norwich, North Cumbria University Hospital, North Wales Cancer Treatment Centre,
Northampton General Hospital, Northern Centre for Cancer Care, Northern Ireland Cancer Centre, Nottingham University Hospital, Peterborough Hospital, Poole Hospital, Queen Alexandra, Portsmouth, Queens Barking, Havering and Redbridge, Queen’s Centre for Oncology & Haematology, Hull, Raigmore Hospital, Royal Berkshire, Royal Cornwall Hospital, Royal Derby Hospital, Royal Devon and Exeter, Royal Free, Royal Marsden, Sutton, Royal Marsden, London, Royal Preston Hospital, Royal Shrewsbury Hospital, Royal Surrey County Hospital, Royal United Hospital, Bath, Southampton University, Southend Hospital, St Bartholomew’s, St James’s Institute of Oncology, Sussex Cancer Centre, Swansea, The Beacon Centre, The Christie, The London Clinic, Torbay Hospital, University College London Hospital, University Hospital North Staffordshire, University Hospital Leicester, Velindre Cancer Centre, Weston Park Hospital.
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Clinical Oncology journal homepage: www.clinicaloncologyonline.net
Original Article
Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK F. Abolaban *y, S. Zaman y, J. Cashmore z, A. Nisbet yx, C.H. Clark x{ * Nuclear
Engineering Department, King Abdulaziz University, Jeddah, Saudi Arabia Department of Physics, University of Surrey, Guildford, UK z Hall-Edwards Radiotherapy Research Group, University Hospital Birmingham, Birmingham, UK x Department of Medical Physics, Royal Surrey County Hospital, Guildford, UK { National Physical Laboratory, Teddington, UK y
Received 18 September 2015; received in revised form 8 December 2015; accepted 5 January 2016
Abstract Aims: Between 2012 and 2014 the number of patients treated in the UK with intensity-modulated radiotherapy (IMRT) techniques increased significantly. One reason for this was the radiotherapy innovation fund for the centres in England. Before the announcement of the fund, a survey of radiotherapy centres was carried out in 2012 which collected data on IMRT uptake, obstacles to implementation, equipment used, delivery techniques and verification methods. A repeat survey was carried out in 2014 to identify key changes to IMRT quality assurance and verification practices. Materials and methods: An online questionnaire was sent out to all 65 UK radiotherapy centres in the summer of 2012 and again in the summer of 2014. Questions covered background and equipment, machine tolerance and quality assurance, machine-based verification, software-based verification and future plans. Results: There have been significant changes in the delivery techniques used for IMRT, with more than twice as many centres reporting the use of volumetricmodulated arc therapy techniques in 2014 compared with 2012. This has been combined with an increase in Monte Carlo-based algorithms in treatment planning systems. In 2012 all centres reported the need to carry out machine-based measurements for IMRT plan verification, dropping to 93% in 2014. Nineteen per cent of centres now report making only one measurement per month for prostate plans and 8% of breast plans never have physical measurements. Most centres use detector arrays for quality assurance measurement (86% in 2012 and 91% in 2014), but a significant number still use film and/or ionisation chambers (51% and 41%). In the analysis of these measurements there has been an increase in the use of tighter criteria. There has been a significant increase in the use of software for verification from 63% in 2012 to 95% in 2014. All centres reported that they needed further resources in order to efficiently achieve the quality assurance required for the number of patients planned to be treated in their centre. Conclusions: The increased numbers of patients being treated with IMRT has meant that there have been significant changes in the way that quality assurance is carried out. These have been mainly in the reduction of measurements and the increase in software-based verification. However, quality assurance is still a significant burden and still has an effect on the numbers of patients who can be treated with IMRT. Crown Copyright Ó 2016 Published by Elsevier Ltd on behalf of The Royal College of Radiologists. All rights reserved.
Key words: IMRT; quality assurance; VMAT
Introduction The uptake of intensity-modulated radiotherapy (IMRT) techniques within the UK was relatively slow compared with some other countries and in August 2012 only 13.6% of radiotherapy patients in England received IMRT [1e3]. Later
Author for correspondence: C. Clark, Department of Medical Physics, Royal Surrey County Hospital, Edgerton Rd, Guildford, Surrey GU2 7XX, UK. E-mail address: [email protected] (C.H. Clark).
that year the Department of Health England created a Radiotherapy Innovation Fund, releasing £23million of funding to cancer centres to increase IMRT capacity. The aim of the fund was to address obstacles to IMRT treatment and to reach a goal of treating more than 24% of all radical radiotherapy patients with IMRT, with this figure already reaching 22.3% by April 2013. It has been suggested that up to 50% of radiotherapy patients may benefit from IMRT [4e6]. Volumetric-modulated arc therapy (VMAT) has now also been introduced to reduce the time taken to deliver IMRT and has been implemented more quickly than static
http://dx.doi.org/10.1016/j.clon.2016.01.013 0936-6555/Crown Copyright Ó 2016 Published by Elsevier Ltd on behalf of The Royal College of Radiologists. All rights reserved.
Please cite this article in press as: Abolaban F, et al., Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK, Clinical Oncology (2016), http://dx.doi.org/10.1016/j.clon.2016.01.013
2
F. Abolaban et al. / Clinical Oncology xxx (2016) 1e7
gantry IMRT was, with over 50% of UK centres now offering this [7]. Thirty-eight per cent of the fund was spent on advanced treatment planning, 22% on linac upgrades, 17% on imageguided radiotherapy equipment and 12% on IMRT and image-guided radiotherapy quality assurance. The remaining (11%) was spent on staffing costs, training, software and immobilisation equipment [8]. The quality assurance burden associated with the implementation of IMRT and VMAT has been considerable and the desire to increase patient numbers means that verification processes play a key role in the extent to which a centre can provide this service [9]. This burden generally falls to the physics department to address. Before the announcement of the fund a survey of radiotherapy centres was carried out in 2012 which collected data on IMRT uptake, obstacles to implementation, equipment used, delivery techniques and verification methods. A repeat survey was carried out in 2014 to identify key changes to IMRT quality assurance and verification practices. Such information may inform centres seeking to increase their IMRT provision further, of potential areas to address and resources required.
Materials and Methods An online questionnaire was sent out at two different time points, July to October 2012 and July to October 2014, to all 65 UK radiotherapy centres. For the purposes of this survey, IMRT was defined to be inverse planned and included all linac-based deliveries (including TomoTherapy and CyberKnife) as well as static and rotating gantry techniques. Questions covered background and equipment, machine tolerance and quality assurance, machine-based verification, software-based verification and future plans.
Results In 2012 and 2014, 96.9% (63/65) and 89.2% (58/65) of centres responded, respectively. A large range of experience was reported from >10 years to only just started. How the Radiotherapy Innovation Fund was used For the English centres, the top three answers for how the Radiotherapy Innovation Fund was spent were treatment planning system (TPS) software (licenses) 88.9%, TPS hardware (51.1%) and delivery hardware (linacs) 44.4%. However, when asked how a further fund would be spent, TPS licences was still the top response (71.4%), second was increasing the number of staff members (57.1%) and on TPS hardware (49.0%) was the third most common answer. Equipment The proportions of centres using linacs from each manufacturer were consistent at the two time points 2012 (2014), being 66% (68% in 2014) Varian (Varian Medical
Systems Inc., Palo Alto, CA, USA), 27% (31%) Elekta (Elekta AB, Stockholm, Sweden), 4% (4%) Siemens (Siemens AG, Erlangen, Germany), 11% (9%) TomoTherapy (AccurayTomo-Therapy, Madison, WI, USA) and 9% (9%) CyberKnife (Accuray-Tomo-Therapy). It should be noted that a number of centres used more than one manufacturer. In 2014 all centres used 6 MV with some use of 10 MV (30% up from 22% in 2012) and a few using 8 MV (3%, same as 2012) and 15 MV (3%, increased from 2% in 2012). There was a shift towards more complex treatment planning algorithms, with an increase in Monte Carlo-based algorithms (from 7.0% to 17.6%) and a reduction in pencil beam methods (23.9% to 14.9%). There was also a significant change in delivery techniques with 74% of centres reporting the use of VMAT techniques (compared with 34% in 2012). There was also a slight reduction in static field IMRT (41% to 35% for dynamic [Varian and CyberKnife] and 49% to 41% for step and shoot) (see Figure 1). Numbers Treated In 2012, 82% of centres reported a limit on the numbers of IMRT patients they were able to treat. This was reported to have dropped to 48% in 2014. Typical reasons given for this were limited resources (TPS and staff), clinician outlining time, machine availability and, of course, the availability of funding for these resources. Timing The survey also asked how long it took to carry out planning and quality assurance for different treatment sites (see Tables 1 and 2). In Figure 2 the total amount of time for head and neck cases shows that overall there was a decrease in the time taken for planning and quality assurance, with a marked decrease in those taking 4þ h and an increase in 1e3 h. Audit There are now a considerable number of external audits available with an IMRT component and 87% of centres have been credentialed to join one of several trials with IMRT in the National Cancer Research Institute portfolio in 2014. Seventy-six per cent took part in the national IMRT audit [10] and 60% in the national rotational IMRT audit [7,11]. More recently there has been an increase in the number of centres participating in interdepartmental audits with IMRT measurements (from 45% in 2012 to 62% in 2014) [12]. Machine Tolerance and Quality Assurance Fifty-five radiotherapy centres responded to the questions about their Multi-leaf collimator (MLC) tests, tolerances and frequencies. The most common test and frequencies with tolerances are given in Table 3. In both 2012 and 2014, about 40% of radiotherapy centres used in-house developed tests for MLC tests, including leaf speed, leaf calibration, dosimetric leaf gap, picket fence test, log files, complex fluences and electronic portal imaging
Please cite this article in press as: Abolaban F, et al., Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK, Clinical Oncology (2016), http://dx.doi.org/10.1016/j.clon.2016.01.013
F. Abolaban et al. / Clinical Oncology xxx (2016) 1e7
3
Which delivery methods do you use for IMRT delivery for Linac based 2012 treatment?
Percentage of response
2014 80% 70% 60% 50% 40% 30% 20% 10% 0%
Fig 1. The proportion of different techniques used for intensity-modulated radiotherapy (IMRT) delivery in 2012 and 2014.
device (EPID)-based field position checks. Whether undertaking published or in-house MLC tests, 56% of centres reported spending less than 1 h doing these measurements. Per Patient Quality Assurance: Measurement In 2012 all centres reported the need to carry out machine-based measurements for IMRT plan verification
for each patient, dropping to 93% in 2014, with four centres stating that they do not do any measurements to check IMRT plans. Overall, measurements-based IMRT quality assurance was most common in head and neck (84%) and lung Stereotactic Ablative Body Radiotherapy (SABR) (82%). However, 19% of centres reported making only one measurement per month for prostate plans and 8% of centres reported breast plans never having physical measurements.
Table 1 Length of time in 2014 taken to plan (excluding contouring and checking) intensity-modulated radiotherapy patients (most frequent answer shown in bold)
Head and neck Prostate Prostate and pelvic nodes Breast Lung Lung SABR Gynaecological Other
1e2 h
2e3 h
3e4 h
4e5 h
1 day
1þ day
Variable
8.2% 68.8% 29.5% 41.7% 33.3% 17.6% 28.9% 20.0%
24.5% 14.6% 22.7% 8.3% 12.5% 11.8% 36.8% 22.9%
16.3% 10.4% 29.5% 16.7% 41.7% 17.6% 15.8% 20.0%
20.4% 4.2% 2.3% 8.3% 4.2% 17.6% 10.5% 8.6%
18.4% 2.1% 11.4% 12.5% 0.0% 23.5% 2.6% 2.9%
8.2% 0.0% 4.5% 4.2% 4.2% 11.8% 2.6% 5.7%
4.1% 0.0% 0.0% 8.3% 4.2% 0.0% 2.6% 20.0%
SABR, Stereotactic Ablative Body Radiotherapy. Table 2 Length of time taken in 2014 to carry out quality assurance for intensity-modulated radiotherapy patients (most frequent answer shown in bold)
Head and neck Prostate Prostate and pelvic nodes Breast Lung Lung SABR Gynaecological Other
0e30 min
30e60 min
1e2 h
2e3 h
3e4 h
4e5 h
5þ h
45.8% 59.6% 48.8% 56.0% 50.0% 22.2% 48.6% 35.3%
35.4% 27.7% 34.9% 32.0% 37.5% 38.9% 37.8% 47.1%
10.4% 10.6% 14.0% 8.0% 12.5% 27.8% 10.8% 14.7%
2.1% 0.0% 0.0% 0.0% 0.0% 11.1% 0.0% 2.9%
2.1% 2.1% 0.0% 0.0% 0.0% 0.0% 2.7% 0.0%
2.1% 0.0% 2.3% 4.0% 0.0% 0.0% 0.0% 0.0%
2.1% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
SABR, Stereotactic Ablative Body Radiotherapy. Please cite this article in press as: Abolaban F, et al., Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK, Clinical Oncology (2016), http://dx.doi.org/10.1016/j.clon.2016.01.013
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F. Abolaban et al. / Clinical Oncology xxx (2016) 1e7
Table 3 Most common MLC tests with frequency and tolerances in 2014 Test
Frequency
Tolerance
Sweeping gap MLC auto recalibration Log file analysis Size of light field Picket fence test Static and dynamic MLC checks VMAT MLC speed test MLC field shape definition Dynamic leaf gap with gantry rotation
Daily Daily Daily Weekly Monthly Monthly Monthly Monthly Monthly
2%
VMAT, volumetric-modulated collimator.
arc
therapy;
MLC,
2 mm 1 mm 1e2 mm 2% e0.3 mm Multi-leaf
Most lung SABR techniques were measured for every patient, but 6% reported having dropped this to one in five or to one per month. Most centres used detector arrays (86% in 2012 and 91% in 2014) or EPID (24% and 26%) for dose distribution measurements. However, a significant number still used film and/or ionisation chambers (51% and 41%). A few centres (5% in 2014) started to use MLC movement log files (dynalog files) for verification of delivery. The most commonly used gamma parameters to analyse the measurements was 3%/3 mm, but for the more complex plans (head and neck, prostate and pelvic node) there was an increase in the use of 3%/2 mm (12% to 20%) and 2%/ 2 mm (0% to 10%) (see Figure 3). In 2012 the split between local and global gamma was 34.8% and 69.8%, respectively (some use both), whereas in 2014 there was a reduction in the use of global gamma to 55.2%. In both surveys there was a range of normalisation points used, with the most common being maximum dose 31.1% in 2012 (15.6% in 2014),
user chosen 24.4% (37.8%) and no normalisation 28.9% (33.3%). The use of global/local evaluation and normalisation methods were mainly influenced by the functionality of the software. In order to define the appropriate tolerances to use, 77.1% (up from 64.3% in 2012) used an in-house data review, 62.5% (50%) consulted the literature, 35.4% (12.5%) used the IPEM report 96 [9] and 4.2% (1.8%) used the same as for their conformal techniques. In 2012, 94% of quality assurance measurements were made by physicists, with the remaining being by technicians or engineers. By 2014 this had changed to 88% by physicists and 6% by radiographers, with the remaining again by technicians or engineers. However, the checking of quality assurance measurements was consistently carried out by physicists. In 2014, 80% of the radiotherapy centres reported that the most common reason for out of tolerance measurements was the plan being too highly modulated. The next most common reasons were that the point dose measured was in a gradient (41%) or that the phantom was not correctly set up (39%); 36.2% never changed a plan based on the results of quality assurance measurements. The final question in the measurement-based quality assurance section was how frequently quality assurance was carried out for each site (see Figure 4 for data from 2014). Prostate treatment was the site where centres had most commonly cut down from measuring every patient. Breast was the most common site where measurements are no longer made. Per Patient Quality Assurance: Calculation There was a significant increase in the use of software for verification from 63% in 2012 to 95% in 2014, with a
Approximately how long does it take to plan (excluding contouring and checking) and do QA for your IMRT Head and neck paƟents?
number of responding centres
14
2012
12
2014
10 8 6 4 2 0 1 - 2 hrs
2 - 3 hrs
3 - 4 hrs
4 - 5 hrs
1 day
1+ day
Variable
Fig 2. Time taken to plan and carry out quality assurance for head and neck intensity-modulated radiotherapy (IMRT). Please cite this article in press as: Abolaban F, et al., Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK, Clinical Oncology (2016), http://dx.doi.org/10.1016/j.clon.2016.01.013
F. Abolaban et al. / Clinical Oncology xxx (2016) 1e7
2014 these were 25%, 12.5% and 37.5%, respectively. Fortytwo per cent of centres cited that they wished to introduce EPID-based quality assurance, introduce more software-based verification (48%) or stop measurements altogether (25%).
Percenatge of respondants
Prostate 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0
2012
Gamma index criteria
Prostate and Pelvic Nodes Percentage of respondants
Discussion
2014
2%/2mm 3%/2mm 3%/3mm 4%/3mm 4%/4mm 5%/5mm
80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0
2012 2014
2%/2mm 3%/2mm 3%/3mm 4%/3mm 4%/4mm 5%/5mm
Gamma index criteria
Head and Neck Percentage of respondants
5
90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0
2012 2014
2%/2mm 3%/2mm 3%/3mm 4%/3mm 4%/4mm 5%/5mm
Gamma index criteria
Fig 3. The gamma index criteria used for the three most common sites, shown in 2012 and 2014.
simultaneous increase of second dose distribution calculations from 9% to 26%. These were predominantly calculated by physicists (74%), but the remainder were carried out by other staff groups (17% dosimetrists, 3% radiographer and 6% other). In contrast with the measurement-based checks being all checked by physicists, 7% of these software calculations are now signed off by dosimetrists. Changes in Quality Assurance Processes In 2012, when asked what changes they wanted to make to their quality assurance process, the most frequent answers were a change in who does the quality assurance (37.8%), a change to a different type of measurement (51.1%) and a reduction in the number of measurements (57.8%). In
The increase in IMRT has been accompanied by a significant increase in the use of VMAT, which increases delivery speed, enabling centres to maintain patient throughput on their linacs. This has in turn meant that more patients can benefit from an IMRT-based treatment, and many centres are now able to deliver IMRT to as many patients as required by their clinical case mix [13]. However, there is still a wide variation in access rate by centre, with four centres not achieving the 24% target by February 2014 and five centres exceeding 40% [6]. This increase has also had an effect on the way quality assurance is carried out and it has been shown that most centres have reviewed their quality assurance approaches in order to absorb this increase. An increase in experience and confidence has also allowed a change in the way quality assurance is undertaken. Overall there has been a reduction in the time needed to plan and quality assurance, which has also been aided by the upgrades in the TPSs, which have included implementation of more advanced algorithms as well as increased computing power. The increase in experience and confidence in local quality assurance results has also led to an increase in inhouse review of gamma tolerances. Overall these have been tightened and there is a move away from the original 3%/3 mm towards a tighter distance to agreement value of 2 mm. This may mean that delivery is becoming more accurate with smoother VMAT deliveries or could also be due to greater experience in planning and quality assurance. However, the developments in the quality assurance tools such as the detector arrays, have also increased the passing rates, due to better resolution and interpolation methods between the measurement points. The burden of patient-specific quality assurance is still considerable for the physics staff groups, but there is now some sharing with other staff groups and streamlining of the timing of quality assurance into the working day. Methods such as EPID dosimetry shorten the set-up time for quality assurance equipment, allowing a quicker measurement to be made, often accompanied by offline analysis by different staff groups at a later time. There has been a significant increase in software-based verification, allowing both point doses and, in some cases, dose distributions to be analysed without need of the linac. This is expected as it is in line with international recommendations [14,15]. The tumour sites where this is most commonly seen (breast and prostate) are generally more straightforward to plan and hence a reduction in measurement as experience increases is appropriate and all centres should consider this move once they have sufficient experience. The move towards calculation-based
Please cite this article in press as: Abolaban F, et al., Changes in Patterns of Intensity-modulated Radiotherapy Verification and Quality Assurance in the UK, Clinical Oncology (2016), http://dx.doi.org/10.1016/j.clon.2016.01.013
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F. Abolaban et al. / Clinical Oncology xxx (2016) 1e7
Fig 4. Frequency of performing machine-based quality assurance, by site, in 2014.
verification also indicates a trend towards a wider staff base and responsibility.
Conclusions Improved resources have increased the numbers of patients being treated with IMRT, but a further increase in both staff numbers and TPS hardware and software is cited as required for a further increase in capacity. There have been significant changes in the way that quality assurance is carried out. These have been mainly in a reduction in measurements and an increase in software-based verification. This has been aided in English centres by the Radiotherapy Innovation Fund, but quality assurance is still a significant burden and still has an effect on the numbers of patients who can be treated with IMRT.
Acknowledgements This work was supported by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under grant no. (D1435-605-135). The authors therefore gratefully acknowledge the DSR technical and financial support. The authors would like to thank the medical physicists in the following hospitals for taking the time to complete the survey: Aberdeen Royal Infirmary, Addenbrooke’s, Arden Cancer Centre, Beatson West of Scotland Cancer Centre, Bristol Haematology and Oncology Centre, Churchill Hospital, University Hospital Birmingham, Cheltenham Hospital, Clatterbridge Cancer Centre, Colchester Hospital, Derriford Hospital, Edinburgh Cancer Centre, Guy’s & St Thomas, Imperial College, Ipswich Hospital, James Cook University Hospital, Kent Oncology Centre, Lincoln Oncology Centre, Mount Vernon Cancer Centre, Ninewells Hospital, Norfolk & Norwich, North Cumbria University Hospital, North Wales Cancer Treatment Centre,
Northampton General Hospital, Northern Centre for Cancer Care, Northern Ireland Cancer Centre, Nottingham University Hospital, Peterborough Hospital, Poole Hospital, Queen Alexandra, Portsmouth, Queens Barking, Havering and Redbridge, Queen’s Centre for Oncology & Haematology, Hull, Raigmore Hospital, Royal Berkshire, Royal Cornwall Hospital, Royal Derby Hospital, Royal Devon and Exeter, Royal Free, Royal Marsden, Sutton, Royal Marsden, London, Royal Preston Hospital, Royal Shrewsbury Hospital, Royal Surrey County Hospital, Royal United Hospital, Bath, Southampton University, Southend Hospital, St Bartholomew’s, St James’s Institute of Oncology, Sussex Cancer Centre, Swansea, The Beacon Centre, The Christie, The London Clinic, Torbay Hospital, University College London Hospital, University Hospital North Staffordshire, University Hospital Leicester, Velindre Cancer Centre, Weston Park Hospital.
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