Radiotherapy and Oncology 109 (2013) 342–343
Contents lists available at ScienceDirect
Radiotherapy and Oncology journal homepage: www.thegreenjournal.com
Editorial
Treatment planning studies in radiotherapy Slav Yartsev a,⇑, Ludvig P. Muren b, David I. Thwaites c a London Regional Cancer Program, London Health Sciences Centre, Canada; b Dept of Medical Physics, Aarhus University/Aarhus University Hospital, Denmark; c Institute of Medical Physics, School of Physics, University of Sydney, Australia
Technological development in radiotherapy (RT) provides new opportunities and treatment options for cancer patients. Sophisticated RT delivery platforms using e.g. different flavours of intensity-modulated radiation therapy (IMRT) call for labour-intensive planning and quality assurance procedures for delivery. During the past years, a number of so-called treatment planning comparison studies in RT have been published, reporting treatment planning results for specific disease sites comparing the established with one or more emerging RT delivery options. According to a PubMed search for the key words ‘‘Tomotherapy/VMAT/RapidArc/SmartArc AND plan’’, referring to studies of rotational IMRT delivery [1–5], the number of such publications has been increasing considerably (Fig. 1). In these studies, the authors typically selected a group of patients (usually between 5 and 15 cases), with more or less similar disease site and stage, and planned RT on these cases using different treatment modalities [6–16]. The results are often presented as side by side images of isodose charts for one ‘‘representative’’ patient, dose volume histograms (DVH) averaged for all patients in the studied cohort, as well as several tables reporting selected DVH endpoints for organs at risk (OARs) and planning target volume (PTV) with the conformity/homogeneity indices added for the latter. Authors usually stress that all plans for the considered techniques are clinically acceptable, but some parameters or the treatment delivery time are better for one of the investigated modalities. There are three main groups of interested readers of treatment planning comparing studies. The first group includes radiation oncologists who are mainly interested in advice as to which technology would be preferential for treatment of a particular patient. Presenting the planning comparisons averaged across a population of patients is not very helpful for this task, especially when the data spread can be quite large. Careful analysis or description of relevant patient-specific features would be highly useful in this respect. Another important issue for a physician is the comparison of the clinical outcome following treatment with the various techniques; usually such information is not available at the time of publication, or at least only in the form of early clinical data (e.g. acute effects). The longer-term clinical outcome of such studies could be published later, however, it would be very interesting if a form of open database for sharing of clinical outcome data could ⇑ Corresponding author. Address: London Regional Cancer Program, London Health Sciences Centre, London, ON, Canada. E-mail address: [email protected] (S. Yartsev). 0167-8140/$ - see front matter Ó 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.radonc.2013.11.008
be created. Searching such a database on a certain disease site and stage (e.g. breast/left-sided/internal mammary node involvement) could provide very useful advice on the preferred treatment modality, combining references to the relevant plan comparison publications and the results of clinical trials. Another group of readers of treatment planning studies are medical physicists involved in the clinical introduction/implementation of new RT modalities. For physicists, the studies should provide a thorough basis for decision-making in this process, and a major concern is the degree to which the results of the plan comparisons can be generalised. In physics, one of the principal requirements for publishing experimental results is their reproducibility in other laboratories. So any experiment should be described in sufficient detail to allow for a repetition of this experiment elsewhere. This is usually not the case for planning ‘‘experiments’’ in medical physics: publications do not provide enough data for others to repeat the calculations. Any plan comparison should contain information about all relevant parameters, including calculation grid (voxel size), a list of the parameters/constraints used for planning and their weights, the number of iterations in the inverse planning optimization procedure, treatment beam-on time, and gantry rotation period. Usually, journals are limiting the details that can be included in the body of the manuscript, however, information of this type, as well as data such as CT studies and structure sets could be made available in supplementary materials, also allowing for re-planning using different techniques or different optimization parameters in order to find optimal and reproducible class solutions. Secondly, availability of data about employed field parameters, optimization constraints and other details needed for calculation permits a re-calculation of this plan on other machine as a QA test for the calculation procedure. Availability of CT and regions of interest data with sufficient information about the planning procedure will also be a useful education and training tool. A third group of readers includes treatment planners who need solid information about the details of the planning procedure applicable to the current case. Unfortunately, there is a variety of definitions and a confusion in terminology that makes it difficult to compare publications of plans performed by different groups. For example, we have found nine different definitions used to describe conformity of the prescribed dose to the target, and seventeen (!) for the homogeneity of dose distribution within the target. The included DVHs should be reproduced in high-quality, allowing for exact numerical values to be derived. It is also essen-
Editorial / Radiotherapy and Oncology 109 (2013) 342–343
Fig. 1. Number of publications per year for rotational IMRT planning studies. (The data for 2013 is limited to 11 months.)
tial that the calculation grid is reported, since reports of the minimum and maximum dose (defined as the extreme dose per voxel) are highly depending on the voxel size used in different treatment planning systems/studies. Reporting of D1% and D99% as the minimum and maximum dose, respectively, should be encouraged, in particular for relatively large structures. For small structures, however, use of dose to specific volumes (1 cm3 for the eyes and 2 cm3 for other structures) is more appropriate. In conclusion, planning studies can provide highly useful information for introduction of new RT modalities, however, it is essential that authors of such studies carefully considers the scope and level of details provided in their submissions, in order to maximise the usefulness of published treatment planning studies in RT.
References [1] Mackie TR, Holmes T, Swerdloff S, et al. Tomotherapy: a new concept for the delivery of dynamic conformal radiotherapy. Med Phys 1993;20:1709–19.
343
[2] Yu CX. Intensity-modulated arc therapy with dynamic multileaf collimation: an alternative to tomotherapy. Phys Med Biol 1995;40:1435–49. [3] Yu CX, Li XA, Ma L, et al. Clinical implementation of intensity-modulated arc therapy. Int J Radiat Oncol Biol Phys 2002;53:453–63. [4] Otto K. Volumetric modulated arc therapy: IMRT in a single gantry arc. Med Phys 2008;35:310–7. [5] Yu CX, Tang G. Intensity-modulated arc therapy: principles, technologies and clinical implementation. Phys Med Biol 2011;56:R31–54. [6] Cozzi L, Dinshaw KA, Shrivastava SK, et al. A treatment planning study comparing volumetric arc modulation with RapidArc and fixed field IMRT for cervix uteri radiotherapy. Radiother Oncol 2008;89:180–91. [7] Palma D, Vollans E, James K, et al. Volumetric modulated arc therapy for delivery of prostate radiotherapy: comparison with intensity-modulated radiotherapy and three-dimensional conformal radiotherapy. Int J Radiat Oncol Biol Phys 2008;72:996–1001. [8] Guckenberger M, Richter A, Krieger T, Wilbert J, Baier K, Flentje M. Is a single arc sufficient in volumetric-modulated arc therapy (VMAT) for complexshaped target volumes? Radiother Oncol 2009;93:259–65. [9] Kjaer-Kristoffersen F, Ohlhues L, Medin J, Korreman S. RapidArc volumetric modulated therapy planning for prostate cancer patients. Acta Oncol 2009;48:227–32. [10] Kuijper IT, Dahele M, Senan S, Verbakel WF. Volumetric modulated arc therapy versus conventional intensity modulated radiation therapy for stereotactic spine radiotherapy: a planning study and early clinical data. Radiother Oncol 2010;94:224–8. [11] Fogliata A, Bergström S, Cafaro I, et al. Cranio-spinal irradiation with volumetric modulated arc therapy: a multi-institutional treatment experience. Radiother Oncol 2011;99:79–85. [12] Scorsetti M, Bignardi M, Alongi F, et al. Stereotactic body radiation therapy for abdominal targets using volumetric intensity modulated arc therapy with RapidArc: feasibility and clinical preliminary results. Acta Oncol 2011;50:528–38. [13] Ost P, Speleers B, De Meerleer G, et al. Volumetric arc therapy and intensitymodulated radiotherapy for primary prostate radiotherapy with simultaneous integrated boost to intraprostatic lesion with 6 and 18 MV: a planning comparison study. Int J Radiat Oncol Biol Phys 2011;79:920–6. [14] Chan OS, Lee MC, Hung AW, Chang AT, Yeung RM, Lee AW. The superiority of hybrid-volumetric arc therapy (VMAT) technique over double arcs VMAT and 3D-conformal technique in the treatment of locally advanced non-small cell lung cancer – a planning study. Radiother Oncol 2011;101:298–302. [15] Stieler F, Wolff D, Schmid H, Welzel G, Wenz F, Lohr F. A comparison of several modulated radiotherapy techniques for head and neck cancer and dosimetric validation of VMAT. Radiother Oncol 2011;101:388–93. [16] Lu SH, Cheng JC, Kuo SH, et al. Volumetric modulated arc therapy for nasopharyngeal carcinoma: a dosimetric comparison with TomoTherapy and step-and-shoot IMRT. Radiother Oncol 2012;104:324–30.
Contents lists available at ScienceDirect
Radiotherapy and Oncology journal homepage: www.thegreenjournal.com
Editorial
Treatment planning studies in radiotherapy Slav Yartsev a,⇑, Ludvig P. Muren b, David I. Thwaites c a London Regional Cancer Program, London Health Sciences Centre, Canada; b Dept of Medical Physics, Aarhus University/Aarhus University Hospital, Denmark; c Institute of Medical Physics, School of Physics, University of Sydney, Australia
Technological development in radiotherapy (RT) provides new opportunities and treatment options for cancer patients. Sophisticated RT delivery platforms using e.g. different flavours of intensity-modulated radiation therapy (IMRT) call for labour-intensive planning and quality assurance procedures for delivery. During the past years, a number of so-called treatment planning comparison studies in RT have been published, reporting treatment planning results for specific disease sites comparing the established with one or more emerging RT delivery options. According to a PubMed search for the key words ‘‘Tomotherapy/VMAT/RapidArc/SmartArc AND plan’’, referring to studies of rotational IMRT delivery [1–5], the number of such publications has been increasing considerably (Fig. 1). In these studies, the authors typically selected a group of patients (usually between 5 and 15 cases), with more or less similar disease site and stage, and planned RT on these cases using different treatment modalities [6–16]. The results are often presented as side by side images of isodose charts for one ‘‘representative’’ patient, dose volume histograms (DVH) averaged for all patients in the studied cohort, as well as several tables reporting selected DVH endpoints for organs at risk (OARs) and planning target volume (PTV) with the conformity/homogeneity indices added for the latter. Authors usually stress that all plans for the considered techniques are clinically acceptable, but some parameters or the treatment delivery time are better for one of the investigated modalities. There are three main groups of interested readers of treatment planning comparing studies. The first group includes radiation oncologists who are mainly interested in advice as to which technology would be preferential for treatment of a particular patient. Presenting the planning comparisons averaged across a population of patients is not very helpful for this task, especially when the data spread can be quite large. Careful analysis or description of relevant patient-specific features would be highly useful in this respect. Another important issue for a physician is the comparison of the clinical outcome following treatment with the various techniques; usually such information is not available at the time of publication, or at least only in the form of early clinical data (e.g. acute effects). The longer-term clinical outcome of such studies could be published later, however, it would be very interesting if a form of open database for sharing of clinical outcome data could ⇑ Corresponding author. Address: London Regional Cancer Program, London Health Sciences Centre, London, ON, Canada. E-mail address: [email protected] (S. Yartsev). 0167-8140/$ - see front matter Ó 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.radonc.2013.11.008
be created. Searching such a database on a certain disease site and stage (e.g. breast/left-sided/internal mammary node involvement) could provide very useful advice on the preferred treatment modality, combining references to the relevant plan comparison publications and the results of clinical trials. Another group of readers of treatment planning studies are medical physicists involved in the clinical introduction/implementation of new RT modalities. For physicists, the studies should provide a thorough basis for decision-making in this process, and a major concern is the degree to which the results of the plan comparisons can be generalised. In physics, one of the principal requirements for publishing experimental results is their reproducibility in other laboratories. So any experiment should be described in sufficient detail to allow for a repetition of this experiment elsewhere. This is usually not the case for planning ‘‘experiments’’ in medical physics: publications do not provide enough data for others to repeat the calculations. Any plan comparison should contain information about all relevant parameters, including calculation grid (voxel size), a list of the parameters/constraints used for planning and their weights, the number of iterations in the inverse planning optimization procedure, treatment beam-on time, and gantry rotation period. Usually, journals are limiting the details that can be included in the body of the manuscript, however, information of this type, as well as data such as CT studies and structure sets could be made available in supplementary materials, also allowing for re-planning using different techniques or different optimization parameters in order to find optimal and reproducible class solutions. Secondly, availability of data about employed field parameters, optimization constraints and other details needed for calculation permits a re-calculation of this plan on other machine as a QA test for the calculation procedure. Availability of CT and regions of interest data with sufficient information about the planning procedure will also be a useful education and training tool. A third group of readers includes treatment planners who need solid information about the details of the planning procedure applicable to the current case. Unfortunately, there is a variety of definitions and a confusion in terminology that makes it difficult to compare publications of plans performed by different groups. For example, we have found nine different definitions used to describe conformity of the prescribed dose to the target, and seventeen (!) for the homogeneity of dose distribution within the target. The included DVHs should be reproduced in high-quality, allowing for exact numerical values to be derived. It is also essen-
Editorial / Radiotherapy and Oncology 109 (2013) 342–343
Fig. 1. Number of publications per year for rotational IMRT planning studies. (The data for 2013 is limited to 11 months.)
tial that the calculation grid is reported, since reports of the minimum and maximum dose (defined as the extreme dose per voxel) are highly depending on the voxel size used in different treatment planning systems/studies. Reporting of D1% and D99% as the minimum and maximum dose, respectively, should be encouraged, in particular for relatively large structures. For small structures, however, use of dose to specific volumes (1 cm3 for the eyes and 2 cm3 for other structures) is more appropriate. In conclusion, planning studies can provide highly useful information for introduction of new RT modalities, however, it is essential that authors of such studies carefully considers the scope and level of details provided in their submissions, in order to maximise the usefulness of published treatment planning studies in RT.
References [1] Mackie TR, Holmes T, Swerdloff S, et al. Tomotherapy: a new concept for the delivery of dynamic conformal radiotherapy. Med Phys 1993;20:1709–19.
343
[2] Yu CX. Intensity-modulated arc therapy with dynamic multileaf collimation: an alternative to tomotherapy. Phys Med Biol 1995;40:1435–49. [3] Yu CX, Li XA, Ma L, et al. Clinical implementation of intensity-modulated arc therapy. Int J Radiat Oncol Biol Phys 2002;53:453–63. [4] Otto K. Volumetric modulated arc therapy: IMRT in a single gantry arc. Med Phys 2008;35:310–7. [5] Yu CX, Tang G. Intensity-modulated arc therapy: principles, technologies and clinical implementation. Phys Med Biol 2011;56:R31–54. [6] Cozzi L, Dinshaw KA, Shrivastava SK, et al. A treatment planning study comparing volumetric arc modulation with RapidArc and fixed field IMRT for cervix uteri radiotherapy. Radiother Oncol 2008;89:180–91. [7] Palma D, Vollans E, James K, et al. Volumetric modulated arc therapy for delivery of prostate radiotherapy: comparison with intensity-modulated radiotherapy and three-dimensional conformal radiotherapy. Int J Radiat Oncol Biol Phys 2008;72:996–1001. [8] Guckenberger M, Richter A, Krieger T, Wilbert J, Baier K, Flentje M. Is a single arc sufficient in volumetric-modulated arc therapy (VMAT) for complexshaped target volumes? Radiother Oncol 2009;93:259–65. [9] Kjaer-Kristoffersen F, Ohlhues L, Medin J, Korreman S. RapidArc volumetric modulated therapy planning for prostate cancer patients. Acta Oncol 2009;48:227–32. [10] Kuijper IT, Dahele M, Senan S, Verbakel WF. Volumetric modulated arc therapy versus conventional intensity modulated radiation therapy for stereotactic spine radiotherapy: a planning study and early clinical data. Radiother Oncol 2010;94:224–8. [11] Fogliata A, Bergström S, Cafaro I, et al. Cranio-spinal irradiation with volumetric modulated arc therapy: a multi-institutional treatment experience. Radiother Oncol 2011;99:79–85. [12] Scorsetti M, Bignardi M, Alongi F, et al. Stereotactic body radiation therapy for abdominal targets using volumetric intensity modulated arc therapy with RapidArc: feasibility and clinical preliminary results. Acta Oncol 2011;50:528–38. [13] Ost P, Speleers B, De Meerleer G, et al. Volumetric arc therapy and intensitymodulated radiotherapy for primary prostate radiotherapy with simultaneous integrated boost to intraprostatic lesion with 6 and 18 MV: a planning comparison study. Int J Radiat Oncol Biol Phys 2011;79:920–6. [14] Chan OS, Lee MC, Hung AW, Chang AT, Yeung RM, Lee AW. The superiority of hybrid-volumetric arc therapy (VMAT) technique over double arcs VMAT and 3D-conformal technique in the treatment of locally advanced non-small cell lung cancer – a planning study. Radiother Oncol 2011;101:298–302. [15] Stieler F, Wolff D, Schmid H, Welzel G, Wenz F, Lohr F. A comparison of several modulated radiotherapy techniques for head and neck cancer and dosimetric validation of VMAT. Radiother Oncol 2011;101:388–93. [16] Lu SH, Cheng JC, Kuo SH, et al. Volumetric modulated arc therapy for nasopharyngeal carcinoma: a dosimetric comparison with TomoTherapy and step-and-shoot IMRT. Radiother Oncol 2012;104:324–30.
