Multidisciplinary international survey of post-operative radiation therapy practices after nipple-sparing or skin-sparing mastectomy.

Objective: Skin sparing mastectomy (SSM) and nipple-sparing mastectomy (NSM) have entered routine surgical practice for breast cancer, though their oncologic safety has not been established in randomized controlled trials. The aim of this study was to evaluate and compare radiation oncologists' and breast surgeons' opinions concerning the indications of post-operative radiation therapy (PORT) after SSM and NSM.

Methods: Radiation oncologists and breast surgeons from North America, South America and Europe were invited to contribute in this study. A 22-question survey was used to evaluate their opinions.

Results: A total of 550 physicians (298 radiation oncologists and 252 breast surgeons) answered the survey. The majority of responders affirmed that PORT should be performed in early-stage (stages I and II) breast cancer for patients who present with risk factors for relapse after SSM and NSM. They considered age, lymph node involvement, tumor size, extracapsular extension, involved surgical margins, lymphovascular invasion, triple negative receptor status and multicentric presentation as major risk factors. Considering that after SSM and NSM, residual breast tissue can be left behind, the residual tissue considered as acceptable in the context of an oncologic surgery were 1-5 mm for breast surgeons. There is no consensus for the necessity of evaluating residual breast tissue through breast imaging.

Conclusions: Although the indications of PORT after SSM and NSM vary among practitioners, standard risk factors for relapse are considered as important by radiation oncologists and breast surgeons.