Radiotherapy and Oncology xxx (2015) xxx–xxx

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Radiotherapy and Oncology journal homepage: www.thegreenjournal.com

Letter to the Editor Implantable drug delivery systems should be inserted outside radiation therapy fields in breast cancer patients

To the Editor Implantable drug delivery systems (DDS) are extensively used in Oncology. Patients with breast cancer undergo radiation therapy (RT) while chemotherapy is administered. When the patient has positive lymph nodes, the supra-clavicular nodes (SCN) need to be irradiated. This study assesses the dosimetric consequences of the presence of a DDS in an irradiation field as well as the feasibility of inserting the DSS on the contralateral side of the treated breast. There are no published data about the interaction of DDS and breast cancer irradiation. At our Institute, the DDS used (HeliositeÒ, Vygon, Paris, France) include a titanium cylindrical pellet of 8 mm diameter (encased in silicon) in order to prevent injuring the patient when inserting the needle. A clinical workflow was designed so that the physician inserting the DDS (at our Institute, the Anesthetist) was aware of the geometry of RT treatment fields for each patient. When clinically possible, the Anesthetist should insert the DDS on the contralateral side of the treated breast. GafchromicÒ EBT films were placed between slabs of a solid water phantom, in a direction that was parallel to the direction of the electron or photon beam. The DDS was positioned flat on top of the phantom. Two beam qualities were used: electrons of 12 MeV and photons of 4 MV, as they represent the beam qualities that are mostly used to irradiate supra clavicular nodes. Gafchromic films were scanned with a Vidar scanner and dose profiles were extracted at a depth of 2.7 cm representative of the average clinical depth of SCN. We retrospectively looked at fifty consecutive breast patients with 24 left side breast cancers. In 100% of cases the implantable port was inserted on the opposite side of the treated breast: 24

http://dx.doi.org/10.1016/j.radonc.2015.04.016 0167-8140/Ó 2015 Published by Elsevier Ireland Ltd.

were placed on the right side of the patient, and 24 on the left side. There were 2 cases of bilateral breast cancers, of them only one with supra-clavicular RT fields. In her case the implantable port was placed at distance from the upper field border. Film measurements have shown that the DDS provoked an under dosage of up to 45% of the prescribed dose with electrons and up to 15% with photons due to the presence of titanium in the device. Moreover the dose distribution underneath the DDS was very inhomogeneous. Positioning the DDS on the opposite side of the radiation fields when clinically possible is feasible and is recommended. It was possible to design a workflow that allowed the anesthetist or surgeon to anticipate on which side the port should be implanted and discussion with the radiation oncologist is needed before the procedure. For the clinical cases where the DDS could not be placed outside the treated areas, dosimetric considerations must be given: the use of electrons should be avoided and a special care should be given to treatment planning to compensate for under dosage. Kim Cao Krassen Kirov Nathalie Fournier-Bidoz Irene Kriegel Youlia M. Kirova Institut Curie, Paris, France Received 29 April 2015 Accepted 29 April 2015 Available online xxxx

Implantable drug delivery systems should be inserted outside radiation therapy fields in breast cancer patients.

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