Chest wall irradiation has no effect on 10-year survival for intermediate-risk breast cancer

Chest wall irradiation has no effect on 10-year survival for intermediate-risk breast cancer

Patients with intermediate-risk breast cancer had similar 10-year overall survival rates whether or not they had undergone chest wall irradiation (CWI) after a mastectomy. This is according to the results of the BIG 2-04 MRC SUPREMO clinical trial, presented at the San Antonio Breast Cancer Symposium (SABCS), from December 10 to 13, 2024.

While CWI after mastectomy is the standard of care for most patients with early-stage breast cancer who have four or more positive axillary lymph nodes, its role in patients with fewer positive lymph nodes or node-negative disease remains controversial.”

Ian Kunkler, MA, MB BChir, professor at the University of Edinburgh and moderator of the study

He explained that although guidelines vary, CWI is often used to treat breast cancer patients with intermediate risk recurrence, such as grade 3 histology and/or lymphovascular invasion.

To evaluate the effects of CWI after mastectomy in patients with intermediate-risk breast cancer, Kunkler and colleagues conducted the phase III clinical trial BIG 2-04 MRC SUPREMO. Patients from several countries took part in the international study:

• Brusttumoren mit einem Durchmesser von 50 mm oder weniger (pT1-2) und einem bis drei positiven axillären Lymphknoten (N1);
• Brusttumoren mit einem Durchmesser von mehr als 50 mm (pT3) und nodalnegativer Erkrankung (N0); oder
• Brusttumoren größer als 20 mm, aber nicht größer als 50 mm im Durchmesser (pT2), N0-Krankheit und Histologie Grad 3 und/oder lymphovaskuläre Invasion.

Of the 1,607 patients available for analysis after exclusion for ineligibility and discontinuation, 808 were randomly assigned to CWI after mastectomy (CWI arm), and 799 patients were randomly assigned to CWI after mastectomy (no CWI arm); Patients also received guideline-concordant axillary node removal and systemic treatments.

There were no significant differences in overall survival between those who received CWI and those who did not receive CWI, as 81.4% and 82.0% of patients in the CWI arm and no CWI arm, respectively, were alive after a median follow-up of 9.6 years. Although CWI reduced the risk of chest wall recurrence by more than half, the absolute rate of chest wall recurrence fell by less than 2%, which Kunkler said was a clinically insignificant difference.

When researchers analyzed the effects of CWI on specific subgroups of patients, they found that neither patients with N0 disease nor those with N1 disease had survival benefits from CWI, suggesting that foregoing CWI after mastectomy may be safe even for patients with node-positive disease.

“This study shows that CWI after mastectomy has no impact on the 10-year overall survival of patients with intermediate-risk breast cancer,” said Kunkler. “The results are important considerations for shared decision-making discussions between patients and physicians, as many patients who are candidates for CWI after mastectomy may not need the treatment.”

Limitations of the study included the small number of patients with pT3 and N0 disease and better overall survival than expected.

The study was funded by a partnership of the Medical Research Council (MRC) and the National Institute for Health and Care Research (NIHR), the European Organization for Research and Treatment of Cancer (EORTC), the EORTC Breast Cancer Group, the Dutch Cancer Society and Cancer Australia. HSBC Trustees, Breast Cancer Institute of Edinburgh, Edinburgh Cancer Center Endowments and University of Edinburgh. Kunkler declares no conflicts of interest.

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