# Anatomical assessment of local recurrence site in breast cancer patients after breast reconstruction and post-mastectomy radiotherapy: implications for radiation volumes and techniques

## TL;DR

This study examines where breast cancer recurs in patients who had mastectomy, reconstruction, and radiotherapy, to improve radiation targeting and outcomes.

## Contribution

The study identifies specific anatomical sites of local recurrence after breast reconstruction and PMRT, informing radiation volume adjustments.

## Key findings

- Local recurrences mainly occurred above the expander/prosthesis, not under it.
- Subcutaneous tissues should be included in target volumes for better local control.
- Neoadjuvant chemotherapy, LVI, and tumor size were linked to worse survival outcomes.

## Abstract

Post-mastectomy radiotherapy (PMRT) improves local control rates and survival in patients with adverse prognostic features. The dose coverage to target volumes is critical to yield maximum benefit to treated patients, increasing local control and reducing risk of toxicity. This study aims to assess patterns of breast cancer relapse in patients treated with mastectomy, breast reconstruction and PMRT.

Breast cancer patients treated with PMRT between 1992 and 2017 were retrospectively reviewed. Clinical and pathological characteristics of patients were collected. Recurrences were defined as “in field,” “marginal” or “out of field.” Survival analyses were performed in relation to progression-free survival (PFS) and overall survival (OS). Correlation between baseline features was explored.

Data of 140 patients are collected. After a median follow-up time of 72 months, median PFS and OS of 63 and 74 months were detected, respectively. Neoadjuvant chemotherapy, lympho-vascular space invasion (LVI) and size of primary tumor were all significantly associated with worst PFS and OS. Ten patients developed local recurrence: 30% "in field," 30% marginal recurrences, 20% "out of field" and 20% both “in field” and “out of field.” No recurrence was detected under the expander, 80% above the device and 20% patients relapsed on IMN chain. The mean distant relapse-free survival was 39 months. Overall, 39 of 140 patients developed distant metastases.

The onset of local–regional relapses occurred mainly above the expander/prosthesis, underlying the importance of inclusion of the subcutaneous tissues within the target volume. In order to refine new contouring recommendations for PMRT and breast reconstruction, future prospective studies are needed.