# Trends in Surgical Treatment for cT4 Breast Cancer After Neoadjuvant Systemic Therapy: A Nationwide Study in The Netherlands

## TL;DR

This study shows that less invasive surgery for advanced breast cancer is linked to better survival rates compared to traditional mastectomy.

## Contribution

The study demonstrates that de-escalated surgery is associated with improved survival compared to modified radical mastectomy for cT4 breast cancer.

## Key findings

- Modified radical mastectomy rates decreased from 78% to 54% for cT4a-c and from 82% to 70% for cT4d breast cancer over time.
- De-escalated surgery was associated with better overall survival than MRM for both cT4a-c and cT4d breast cancer.
- Five-year crude relative survival was higher for de-escalated treatment compared to MRM in both cT4a-c and cT4d patients.

## Abstract

Current guidelines recommend neoadjuvant systemic therapy (NST) followed by modified radical mastectomy (MRM) for stage T4 breast cancer. In this study, trends in MRM and de-escalated surgery of cT4a-c and cT4d breast cancer were evaluated and the impact of treatment on survival was assessed.

Patients with cT4NanyM0 breast cancer who received NST between 1989 to 2020 were selected from the Netherlands Cancer Registry. Rates of MRM and de-escalated breast/axillary surgery were analyzed for the periods 1989–1999, 2000–2009, and 2010–2020. Cox proportional hazard regression with inverse probability weighing was used to estimate for confounding-adjusted hazard ratios (HRs) for overall survival. Crude relative survival was calculated using excess mortality ratios from national life tables.

This study included 2,541 patients with cT4a-c and 1479 with cT4d breast cancer. The frequency of MRM decreased from 78% in 1989–1999 to 54% in 2010–2020 for cT4a-c and from 82% to 70% for cT4d patients. De-escalated surgery was associated with better overall survival than MRM, for both cT4a-c (HR 0.74, 95% confidence interval [CI] 0.63–0.87) and cT4d breast cancer (HR 0.78, 95% CI 0.63–0.96). Five-year crude relative survival for MRM versus de-escalated treatment was 66% (95% CI 0.64–0.69) versus 83% (95% CI 0.79–0.87) for cT4a-c, and 56% (95% CI 0.53–0.59) versus 70% (95% CI 0.64–0.76) for cT4d.

Modified radical mastectomy rates decreased over time. De-escalated surgery was associated with improved 5-year overall survival compared with MRM. These findings suggest that de-escalated surgery is at least equivalent to MRM in terms of survival and may support consideration of less invasive surgical approaches.

The online version contains supplementary material available at 10.1245/s10434-025-17585-2.