Patients with intermediate-risk breast cancer may be able to safely avoid chest wall irradiation (CWI) after mastectomy without compromising their long-term survival, according to results from the BIG 2-04 MRC SUPREMO clinical trial. The study, presented at the San Antonio Breast Cancer Symposium (SABCS), challenges the standard of care for certain early-stage breast cancer patients. The research, led by Ian Kunkler, MA, MB BChir, a professor at the University of Edinburgh, suggests that CWI does not significantly impact 10-year overall survival in this patient population.
Study Details and Findings
The phase III trial enrolled 1,607 patients with intermediate-risk breast cancer from multiple countries. The criteria included patients with tumors 50 mm or less with one to three positive axillary lymph nodes, tumors larger than 50 mm with node-negative disease, or tumors larger than 20 mm but no larger than 50 mm with node-negative disease and grade 3 histology and/or lymphovascular invasion. Participants were randomized to either receive CWI after mastectomy or to omit CWI, in addition to receiving guideline-concordant axillary node clearance and systemic treatments.
After a median follow-up of 9.6 years, the overall survival rates were similar between the two groups: 81.4% in the CWI arm and 82.0% in the no CWI arm. Although CWI reduced the risk of chest wall recurrence by over half, the absolute rate of chest wall recurrence was reduced by less than 2%, which Kunkler noted was a clinically insignificant difference.
Implications for Clinical Practice
"This study demonstrates that CWI after a mastectomy has no influence on 10-year overall survival for patients with intermediate-risk breast cancer," said Kunkler. He emphasized that the results should be considered during discussions between patients and clinicians, as many patients eligible for post-mastectomy CWI may not require the treatment. The study also found that neither patients with node-negative disease nor those with one to three positive lymph nodes experienced survival benefits with CWI.
Current Guidelines and Controversies
Post-mastectomy CWI is typically the standard of care for patients with early-stage breast cancer who have four or more positive axillary lymph nodes. However, its role in patients with fewer positive lymph nodes or node-negative disease has been a subject of debate. CWI is often used in patients with intermediate-risk breast cancers, defined as those with one to three positive lymph nodes or node-negative patients with factors increasing recurrence risk, such as grade 3 histology or lymphovascular invasion.
Study Limitations
Limitations of the study included the low accrual of patients with pT3, N0 disease and better overall survival than anticipated.
