# Long-term outcomes of volume de-escalation for breast nodal irradiation

## TL;DR

This study examines the long-term effects of reducing radiation volume in breast cancer patients and finds that certain factors predict worse outcomes.

## Contribution

The study provides new insights into the outcomes of volume de-escalation in breast cancer radiotherapy and identifies risk factors for poor survival.

## Key findings

- Lymph node ratio, Luminal B subtype, and triple-negative subtype are significant predictors of poor disease-free survival.
- Loco-regional recurrence occurred in 29.1% of patients, with 5- and 10-year DFS rates of 81.4% and 60.9%, respectively.
- Lymphedema occurred in 9.3% of patients, mostly mild.

## Abstract

NCCN recommendations suggest irradiating chest wall/breast only + regional node irradiation (RNI) of the undissected axillary levels for node-positive breast cancer (BC) patients. We retrospectively analyzed a cohort of node-positive BC patients who received adjuvant radiotherapy (RT) with a volume de-escalation at the level of axillary nodes.

We conducted a retrospective analysis of node-positive BC patients treated with adjuvant RT administered following a conventional fractionation schedule using a 3D-conformal technique to the chest wall or breast and only the IV axillary level. The primary endpoint of the study was disease free survival (DFS). Secondary endpoints included loco-regional control (LRC), and Overall Survival (OS). Toxicity was documented according to the Radiation Therapy Oncology Group (RTOG) criteria.

A total cohort of 343 patients was analyzed. Loco-regional recurrence occurred in 100 (29.1%). The 5- and 10-year Kaplan-Meyer curves for DFS were 81.4% (95% CI: 79.3%–83.5%) and 60.9% (95% CI: 57.6%–64.5%), respectively. Multivariate Cox analysis confirmed that lymph node ratio (HR = 9.76, 95% CI: 3.12–30.53, p = 0.0001), Luminal B subtype (HR = 2.03, 95% CI: 1.26–3.29, p = 0.004), and triple-negative subtype (HR = 2.70, 95% CI: 1.22–5.99, p = 0.01) were significant predictors of poor DFS. Lymphedema in the ipsilateral arm was reported in 32 (9.3%) patients, primarily Grade 1 or 2.

Improved patients’ selection and a broader use of systemic therapy could make de-escalation a feasible option. However, this approach should be avoided in patients with extensive nodal involvement, specific molecular subtypes, or comorbidities that prevent the use of chemotherapy.