Though there are still limited data from small retrospective studies regarding the indications for postmastectomy RT in MBC and its impact on outcome [20–22], a prior retrospective study by Fogh et al., on forty-two male nonmetastatic ER+/PR+ breast cancer patients, showed adjuvant RT and tamoxifen to be superior in terms of overall survival to adjuvant tamoxifen alone, adjuvant RT alone, and no adjuvant therapy, suggesting a possible role for adjuvant RT in addition to tamoxifen in ER+/PR+ MBC [23]. This evidence concerns the gene ESR1 and breast cancer.