Initial Clinical Experience of Postmastectomy Intensity Modulated Proton Therapy in Patients with Breast Expanders with Metallic Ports

Publication date: Available online 16 December 2016
Source:Practical Radiation Oncology
Author(s): Robert W. Mutter, Nicholas B. Remmes, Mohamed MH Kahila, Kathy A. Hoeft, Deanna H. Pafundi, Yan Zhang, Kimberly S. Corbin, Sean S. Park, Elizabeth S. Yan, Valerie Lemaine, Judy C. Boughey, Chris J. Beltran
PurposeThe feasibility of proton post-mastectomy radiotherapy (PMRT) in patients reconstructed with expanders has not been previously reported, limiting treatment options. We analyzed the dosimetric impact of the metallic port contained within expanders on intensity modulated proton therapy (IMPT) and report our techniques and quality control for treating patients in this setting.Methods and Materials12 patients with the same expander model underwent two-field IMPT as part of a prospective registry. All planning dosimetry was checked with an in-house graphic processing unit-based Monte-Carlo simulation. Proton ranges through the expander were validated using a sample implant. Dosimetric impact of setup metallic port position uncertainty was evaluated. Pre and post-treatment photographs were obtained and acute toxicity was graded using the Common Terminology Criteria for Adverse Events, version 4.0.ResultsNine patients had bilateral skin-sparing mastectomy with bilateral tissue expander reconstruction and three patients had unilateral skin-sparing mastectomy and reconstruction. The left side was treated in ten patients and the right side in two. Target coverage and normal tissue dose uncertainties resulting from the expander were small and clinically acceptable. The maximum physician-assessed acute radiation dermatitis was three in one patient, two in five patients and one in six patients.ConclusionsPostmastectomy IMPT in breast cancer patients with expanders is feasible and associated with favorable CTV coverage and normal tissue sparing, even when taking into account treatment uncertainties. Therefore, these patients should be eligible to participate in clinical trials studying the potential role of proton therapy in breast cancer. We caution, however, that institutions should carry out similar analyses of the physical properties and dosimetric impact of the particular expanders used in their practice prior to considering IMPT.



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