Impact of Anterior Margin Status Following Skin- or Nipple-Sparing Mastectomy in Patients Undergoing Implant-Based...

This study aims to increase the evidence guiding the management of positive or close anterior margins for invasive breast cancer or ductal carcinoma in situ after skin- or nipple-sparing mastectomy (SSM/NSM) and implant-based breast reconstruction. Re-excision to clear margins has been recommended but is not always feasible. Post-mastectomy radiotherapy may reduce rates of recurrence but also adversely impacts reconstruction outcomes.

A total of 160 patients undergoing SSM/NSM with immediate direct-to-implant- or two-stage expander-to-implant-based breast reconstruction between March 2012 and September 2022 were retrospectively identified. Final margin status and adjuvant therapies were recorded. Primary outcomes assessed were ipsilateral, regional, and distant recurrence rates. Implant loss rates were assessed as a secondary outcome. Analysis of recurrence rates were performed based on margin status and adjusting for the confounding effects of radiotherapy, chemotherapy, and endocrine treatments.

Positive or close margins were identified in 19% (n=30) and 11% (n=18) of patients, respectively. The median follow-up period was 60 months. The ipsilateral breast cancer recurrence rate was 6% (n=9), the regional recurrence rate was 3% (n=5), and distant metastasis occurred in 6% (n=10). No statistically significant association was found between margin status and recurrence rates. When the anterior margin was positive or close for cancer or ductal carcinoma in situ, the addition of radiotherapy reduced the rates of ipsilateral breast cancer recurrence (odds ratio 0.08; 95% confidence interval 0.01-0.71; p=0.02). Radiotherapy was associated with increased overall rates of unplanned exchange or loss of the initial implant over the study period (relative risk 1.65; 95% confidence interval 1.23-2.22, p<0.001).

Radiotherapy may provide a safe oncologic alternative to management of close anterior margins after SSM/NSM when re-excision is not possible, but it results in increased implant-related complications.