Is higher dose radiation necessary for positive resection margin after breast-conserving surgery for breast cancer?

Background: A positive resection margin after breast-conserving surgery (BCS) usually requires re-excision, which impairs cosmetic outcomes and causes considerable distress. This study aimed to evaluate the prognosis of patients with positive resection margin after BCS and the role of radiation therapy (RT) in these patients. Materials and methods: We analyzed 297 patients who underwent BCS for breast cancer and had invasive carcinoma or ductal carcinoma in situ (DCIS) within less than 1 mm from the resection margin in Samsung Medical Center from January 2000 to June 2012. The association between RT dose and the incidence rate of ipsilateral breast tumor recurrence (IBTR) was examined. Results: After a median follow-up of 78 months, the incidence rate of IBTR in all patients was 4.6% after 5 years. In the multivariate analysis, the unfavorable factors associated with IBTR were age < 40 years (p = 0.019), RT dose (<60 Gy vs. > 66 Gy, p = 0.012; 60–66 Gy vs. > 66 Gy, p = 0.017), and discontinuation of hormone therapy (p = 0.001). Conclusions: Among the patients with invasive carcinoma or DCIS within less than 1 mm from the resection margin, adjuvant RT with higher dose > 66Gy EQD2 might improve local control. Further prospective studies are warranted to validate the benefit and risk of a high dose boost after BCS in patients with a positive resection margin.