SUPREMO Trial (10-Year Analysis)

Background

Phase III randomized trial, N=1600 (primarily pT1-2N1M0 and pT3N0M0 disease), intermediate-risk early breast cancer post-mastectomy. Enrollment was extended with protocol modifications to ensure completion. Evaluates whether postmastectomy chest-wall radiation improves outcomes in intermediate-risk disease.

Interventions and follow up

Arm A: Postmastectomy radiation therapy (PMRT) to chest wall
Arm B: No PMRT
Primary endpoint: Overall survival (OS) at 10 years
mFollow up: 10 years

Results

OS (10-yr): No significant benefit observed with PMRT to chest wall alone
Regional nodal irradiation (RNI): limited use in trial; did not include internal mammary node coverage

Adverse events

Cardiac/pulmonary: cardiotoxicity is a known concern with historical chest-wall PMRT; rates NR in this analysis
Second malignancy: secondary malignancies a recognized late risk of historical PMRT; not detailed in the trial report

Conclusions

SUPREMO 10-year results showed no OS benefit from PMRT to chest wall alone in low- to intermediate-risk disease. However, trial design limitations and evolving systemic therapy standards limit applicability to contemporary practice.

Key Limitations

Reduced sample size and extended accrual compromised statistical power; limited RNI and no internal mammary coverage; broadened eligibility diluted the high-risk population; many patients had node-negative or limited nodal involvement; systemic therapy practices evolved over the trial duration; quality-assurance discrepancies in methodology.

Clinical Context

SUPREMO demonstrates a limited role for chest-wall-only PMRT in intermediate-risk historical cohorts. ASCO/ASTRO and ESMO guidance now supports comprehensive RNI including internal mammary nodes in higher-risk node-positive disease, with biology-driven risk stratification rather than anatomic staging alone. ESMO-MCBS: not applicable (RT trial, OS endpoint).

References