# Omitting radiotherapy in LUMINA-like breast cancer after breast conserving surgery: 10-year results of a population-based cohort study

## TL;DR

A study found that skipping radiotherapy after breast-conserving surgery for low-risk breast cancer leads to slightly higher recurrence rates but no significant survival difference for small tumors.

## Contribution

This study validates and extends the LUMINA trial's findings with a larger population-based cohort and 10-year follow-up data.

## Key findings

- Local recurrence rates were significantly higher in patients who skipped radiotherapy.
- Radiotherapy did not improve breast cancer-specific survival for tumors ≤1.4 cm.
- Recurrence rates remained below 5% in both groups over 10 years.

## Abstract

Recently, the LUMINA trial reported 5-year results of omitting radiotherapy in a low-risk cohort after breast-conserving surgery (BCS). This study aimed to validate their 5-year results and investigate 10-year outcomes of patients satisfying their criteria in a population-based cohort.

A total of 28 185 eligible patients were identified from the Surveillance, Epidemiology and End Results (SEER) database to establish SEER-LUMINA cohort. The Kaplan–Meier method was employed to estimate recurrence incidence and survival outcomes. Matched cohorts were generated using propensity score matching (PSM). The Cox proportional hazards model was used to generate hazard ratios.

A total of 6808 patients of the 28 185 did not receive radiotherapy while 21 377 underwent postoperative radiotherapy. After PSM, each group had 5954 patients, revealing significant differences in local recurrence incidence (no-radiotherapy group 0.65% at 5 years and 3.68% at 10 years vs radiotherapy group 0.14% at 5 years and 1.54% at 10 years, P < .001), breast cancer-specific survival (BCSS) (no-radiotherapy group 98.51% at 5 years and 96.11% at 10 years vs radiotherapy group 99.05% at 5 years and 96.34% at 10 years, P = .028). No difference was observed in BCSS between the 2 groups for SEER-LUMINA patients with tumor ≤1.4 cm (the optimal tumor size cutoff value for BCSS) (P = .099).

Incidence, whether 5-year or 10-year recurrence, was lower than 5% in the SEER-LUMINA cohort. Radiotherapy following BCS reduced the local recurrence statistically significantly for those patients, but the clinical impact of this reduction was modest. Radiotherapy did not result in a difference in BCSS for SEER-LUMINA patients with tumors ≤1.4 cm.