SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. It is estimated that in the US, approximately 310,720 new cases of female breast cancer will be diagnosed in 2024, and about 42,250 individuals will die of the disease, largely due to metastatic recurrence.
Even though the use of postmastectomy radiotherapy has been widely accepted for patients with four or more positive lymph nodes, the role of postmastectomy radiotherapy for those with one to three positive nodes or node-negative disease remains controversial. Nonetheless, post mastectomy chest wall irradiation is commonly used to treat this intermediate risk group of breast cancer patients.
BIG 2-04 MRC SUPREMO trial is a Phase 3, randomized clinical study, conducted to investigate the impact of adjuvant chest wall irradiation (CWI) following mastectomy and axillary surgical staging among patients with operable breast cancer, at intermediate-risk of loco-regional recurrence. Intermediate risk breast cancer patients are those with 1-3 positive lymph nodes or patients who have no positive lymph nodes but whose cancers exhibit other factors that increase the risk of recurrence, such as grade 3 histology and/or lymphovascular invasion. Enrolled patients had breast tumors 5 cm or less (pT1–2) and 1-3 positive axillary lymph nodes (N1), breast tumors larger than 5 cm (pT3) and node-negative disease (N0), or breast tumors larger than 2 cm but no larger than 5 cm (pT2), N0 disease, and grade 3 histology and/or lymphovascular invasion.
Of the 1,607 eligible patients available for analysis 808 patients were randomly assigned to receive chest wall irradiation after mastectomy (chest wall irradiation group), and 799 patients were randomly assigned to omit chest wall irradiation after mastectomy (no chest wall irradiation group). Patients additionally received guideline-based axillary node clearance and systemic therapies. Chest wall Irradiation consisted of a total dose of 50 Gy in 25 daily fractions over 5 weeks or radiobiologically equivalent schedules including 40 Gy in 15 fractions over 3 weeks. Medial periclavicular/ internal mammary nodal irradiation was allowed but axillary irradiation was not permitted.
At a median follow up of 9.6 years, there were no significant differences in Overall Survival between those who received chest wall irradiation and those who did not (81.4% and 82.0%, respectively). Even though chest wall irradiation reduced the risk of chest wall recurrence by over half, the absolute rate of chest wall recurrence was reduced by less than 2%, which was clinically insignificant. Further, neither patients with N0 disease nor those with N1 disease experienced survival benefits with chest wall irradiation, suggesting that even patients with lymph node-positive disease could safely omit post-mastectomy chest wall irradiation.
It was concluded from the primary analysis of the SUPREMO trial that following mastectomy in patients with 1-3 positive nodes, or in node negative breast cancer patients with other risk factors treated with modern therapeutic interventions, chest wall irradiation has no impact on overall survival and has a clinically insignificant impact on chest wall recurrence.
GS2-03: Does postmastectomy radiotherapy in ‘intermediate-risk’ breast cancer impact overall survival? 10 year results of the BIG 2-04 MRC SUPREMO randomised trial: on behalf of the SUPREMO trial investigators. Presented at SABCS 2024; Presenting Author(s): Ian Kunkler; Abstract Number: SESS-3537
