# Impact of bilateral surgery on time to treatment in patients with breast cancer undergoing mastectomy – a retrospective cohort study

## TL;DR

This study found that bilateral mastectomy in breast cancer patients does not delay adjuvant treatment compared to unilateral mastectomy.

## Contribution

The study provides new evidence that bilateral mastectomy does not prolong the time to adjuvant treatment in breast cancer patients.

## Key findings

- Bilateral mastectomy was not associated with a delay in time to adjuvant treatment compared to unilateral mastectomy.
- Bilateral mastectomy was associated with a shorter time to adjuvant chemotherapy.
- Postoperative complications were linked to longer delays in adjuvant treatment.

## Abstract

It is unclear whether patients with breast cancer (BC) who undergo mastectomy experience delays in adjuvant treatment when bilateral surgery is performed. This study was conducted with the objective of addressing this knowledge gap.

Stage 0-III BC patients who underwent mastectomy (including conventional mastectomy, nipple-sparing mastectomy [NSM], and skin-sparing mastectomy [SSM]) at a Swiss university hospital between 01/2013 and 12/2023 were identified from a prospectively maintained database. Multivariable Cox proportional hazards regression models were used to detect predictors of time to adjuvant treatment.

A total of 394 patients were included, 308 (78.2%) of whom underwent unilateral mastectomy (UM) and 86 (21.8%) of whom underwent bilateral mastectomy (BM). Compared with patients who underwent UM, those who underwent BM were younger (median age [years] 49 vs. 60), more likely to carry a pathogenic germline BRCA variant (28.7% vs. 2.6%), presented with bilateral breast cancer (14.9% vs. 0%), and underwent neoadjuvant chemotherapy (34.5% vs. 12.4%). Patients who underwent BM were more likely to receive NSM or SSM (81.4% vs. 52.9%) and to develop wound healing disorders (20.7% vs. 11.4%). On univariable analysis, no differences in time to any adjuvant treatment were observed between BMs and UMs (median [days] 34 vs. 33; p = 0.444). Multivariable analysis suggested that bilateral mastectomy was associated with a shorter time to adjuvant chemotherapy (HR 2.54, 95% CI 1.15–5.58). Short-term postoperative complications were associated with prolonged time to any adjuvant treatment (HR 0.50, 95% CI 0.36–0.71) and time to adjuvant chemotherapy (HR 0.37, 95% CI 0.17–0.79).

Undergoing BM did not result in a delay in time to adjuvant treatment in comparison to UM.