Intensity modulated proton therapy for postmastectomy radiation of bilateral implant reconstructed breasts: a treatment planning study

Delivery of post-mastectomy radiation (PMRT) in women with bilateral implants represents a technical challenge, particularly when attempting to cover regional lymph nodes. Intensity modulated proton therapy (IMPT) holds the potential to improve dose delivery and spare non-target tissues. The purpose of this study was to compare IMPT to three-dimensional (3D) conformal radiation following bilateral mastectomy and reconstruction.

Ten IMPT, 3D conformal photon/electron (P/E), and 3D photon (wide tangent) plans were created for 5 patients with breast cancer, all of whom had bilateral breast implants. Using RTOG guidelines, a physician delineated contours for both target volumes and organs-at-risk. Plans were designed to achieve 95% coverage of all targets (chest wall, IMN, SCV, axilla) to a dose of 50.4 Gy or Gy (RBE) while maximally sparing organs-at-risk.

IMPT plans conferred similar target volume coverage with enhanced homogeneity. Both mean heart and lung doses using IMPT were significantly decreased compared to both P/E and wide tangent planning.

IMPT provides improved homogeneity to the chest wall and regional lymphatics in the post-mastectomy setting with improved sparing of surrounding normal structures for woman with reconstructed breasts. IMPT may enable women with mastectomy to undergo radiation therapy without the need for delay in breast reconstruction.