Fifteen-year results of a randomized phase 3 trial show that for patients with stage I–III breast cancer, internal mammary and medial supraclavicular (IM-MS) lymph node chain irradiation reduces breast cancer mortality and breast cancer recurrence but does not produce a significant improvement in overall survival.
"Ten-year results from several studies showed improved disease-free survival and distant metastasis-free survival, reduced breast cancer-related mortality, and variable effects on overall survival with the addition of partial or comprehensive regional lymph node irradiation after surgery in patients with breast cancer," write the investigators of the European Organisation for Research and Treatment of Cancer (EORTC) 22922/10925 trial in their publication in The Lancet Oncology, led by first author Philip Poortmans, MD, PhD, Professor in the Faculty of Medicine and Health Sciences at the University of Antwerp in Wilrijk-Antwerp, Belgium. For this reason, the researchers investigated the impact of IM-MS irradiation on overall survival.
The EORTC 22922/10925 trial, completed in 46 radiation oncology departments in 13 countries, enrolled women up to 75 years of age with unilateral, histologically confirmed, stage I–III breast adenocarcinoma with involved axillary nodes or a central or medially located primary tumor. Patients underwent either mastectomy or breast-conserving surgery with axillary staging. A total of 4,004 patients were randomized in a 1:1 ratio to receive IM-MS irradiation at 50 Gy in 25 fractions or no IM-MS irradiation, for a primary end point of overall survival in the intention-to-treat population. Secondary end points included disease-free survival, distant metastasis-free survival, breast cancer mortality, breast cancer recurrence, and cause of death. Additional follow-up is planned for 20 years from the time of randomization.
At a median follow-up of 15.7 years, 27.7% of patients in the IM-MS irradiation group and 28.4% of patients in the control group had died. There was no statistically significant difference in overall survival rates: 73.1% for the IM-MS group compared with 70.9% for the control group, with a hazard ratio of 0.95 (95% confidence interval, 0.84–1.06; P=0.36). However, IM-MS did result in a significant reduction in breast cancer recurrence (24.5% vs 27.1%) and breast cancer mortality (16.0% vs 19.8%). No significant differences were seen for disease-free survival (60.8% vs 59.9%) or distant metastasis-free survival (70.0% vs 68.2%). Causes of death were similar between groups.
"The 15-year results show a significant reduction of breast cancer mortality and any breast cancer recurrence by IM-MS irradiation in stage I–III breast cancer," conclude Dr. Poortmans and colleagues. "However, this is not converted to improved overall survival."
For More Information
Poortmans PM, Weltens C, Fortpied C, et al (2020). Internal mammary and medial supraclavicular lymph node chain irradiation in stage I–III breast cancer (EORTC 22922/10925): 15-year results of a randomised, phase 3 trial. Lancet Oncol. [Epub ahead of print] DOI:10.1016/S1470-2045(20)30472-1
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