# Comparison of overall survival and disease-free survival for breast-conserving surgery and mastectomy in breast cancer patients receiving neoadjuvant therapy: a matched case-control study from two institutions

## TL;DR

This study finds that breast-conserving surgery and mastectomy have similar survival outcomes for breast cancer patients after neoadjuvant therapy, but mastectomy may be better for those with positive lymph nodes or over 40 years old.

## Contribution

The study provides new evidence on the oncological safety of breast-conserving surgery versus mastectomy after neoadjuvant therapy using a matched case-control design.

## Key findings

- Breast-conserving surgery and mastectomy showed similar 5-year overall and disease-free survival rates after neoadjuvant therapy.
- Mastectomy was an independent adverse prognostic factor for survival in patients with positive lymph nodes and those over 40 years old.
- Propensity score matching ensured balanced comparison between the two surgical approaches.

## Abstract

Neoadjuvant therapy (NAT) has been increasingly promoted for treating early-stage breast cancer (BC), which significantly improves the adoption of breast-conserving surgery (BCS). However, concerns related to the oncological safety of BCS versus mastectomy remain unelucidated. The present study compared survival outcomes between patients treated with BCS and those treated with mastectomy after NAT through stratified analyses.

The study included female BC patients who underwent radical surgery after NAT at the Peking University First Hospital and Cancer Hospital of Chinese Academy of Medical Sciences from January 2013 to December 2021. Propensity score matching (PSM) was used to minimize the selection bias. Overall survival (OS) and disease-free survival (DFS) were compared between patients receiving BCS and mastectomy.

A total of 994 patients were enrolled, including 285 patients treated with BCS and 709 patients treated with mastectomy. Following PSM, patients were assigned to the BCS (n = 258) and mastectomy (n = 258) groups; these two groups were well balanced regarding clinical and pathological characteristics. The 5-year OS rate (90.5% vs. 95.8%, P = 0.535) and DFS rate (86.3% vs. 86.9%, P = 0.648) of the mastectomy group were identical to those of the BCS group in the matched cohort. Stratified analysis revealed that mastectomy was an independent adverse prognostic factor for OS (hazard ratio [HR]: 2.158, 95% CI: 1.254–4.954, P = 0.034) and DFS (HR: 2.914, 95% CI: 1.713–5.422, P = 0.010) in patients with positive lymph nodes. Additionally, age-based stratification showed that mastectomy was an independent prognostic factor for DFS in BC patients aged > 40 years (HR: 2.471, 95% CI: 1.082–5.643, P = 0.022).

BCS does not affect OS and DFS in BC patients treated with NAT. However, it should be noted that BCS provides a substantial survival benefit as compared to mastectomy in patients with clinically positive lymph nodes and those aged > 40 years.