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.