Identifying Factors Predicting Margin Status After Mastectomy

Introduction A positive margin after mastectomy increases the risk of breast cancer recurrence and the morbidity associated with re-excision or chest wall irradiation. This study aimed to identify factors that may predict margin status after mastectomy. Methods Women with Tis-T3 breast cancers who underwent mastectomy from 2014 to 2020 were retrospectively analyzed. Comparisons of clinicopathologic data were made between patients with negative margins (> 1 mm) and close (<= 1 mm) or positive margins. Results Of 938 women who underwent mastectomy, negative margins were reported for 794 (85%) women, while 144 (15%) women experienced close (97/144, 10%) or positive (47/144, 5%) margins. Re-excision of margins was performed in 37 (26%) of those patients, and 9 (24%) had residual cancer after re-excision. On multivariate analysis, increasing age (odds ratio [OR] 0.97, 95% confidence interval [CI] 0.96-0.99, p = 0.002), increased body mass index (BMI; OR 0.97, 95% CI 0.93-1.00, p = 0.049), and neoadjuvant chemotherapy (NAC; OR 0.44, 95% CI 0.25-0.79, p = 0.006) decreased the risk of close or positive margins. Tumors located in the lower inner quadrant (OR 3.83, 95% CI 1.90-7.72, p < 0.001), multifocal tumors (OR 1.78, 95% CI 1.19-2.66, p = 0.005), immediate reconstruction (OR 1.63, 95% CI 1.03-2.58, p = 0.039), and a preoperative tumor to breast volume ratio > 4.14 (OR 2.66, 95% CI 1.43-4.94, p = 0.002) significantly increased the risk of close or positive margins. Conclusions Age, BMI, tumor location, multifocality, NAC, immediate reconstruction, and tumor to breast volume ratio independently predicted margin status after mastectomy. These data should be considered when counseling women considering mastectomy.