Regional nodal irradiation (RNI) following surgery did not improve invasive disease-free survival in patients with breast cancer at low risk for recurrence, raising questions about the role of RNI in this population.
This secondary analysis of the SWOG S1007 RxPONDER trial included 4871 women with HR-positive, ERBB2-negative breast cancer, 1-3 positive axillary nodes, and a recurrence risk score of no more than 25 out of 100.
The initial SWOG S1007 RxPONDER trial randomly assigned women to endocrine therapy alone or chemotherapy then endocrine therapy following surgery with sentinel-node biopsy or axillary lymph-node dissection.
The secondary analysis assessed locoregional recurrence (LRR) rates with and without RNI over a median follow-up of 6.1 years.
Among nearly 4000 patients who received radiotherapy, 2274 received RNI.
At 5 years, the cumulative incidence of LRR was 0.85% among women who had breast-conserving surgery plus radiotherapy with RNI; 0.55% after breast-conserving surgery with radiotherapy without RNI; 0.11% after mastectomy followed by radiotherapy; and 1.7% after mastectomy without radiotherapy.
Similar low recurrence rates were observed among women who omitted chemotherapy and received endocrine therapy alone.
Invasive disease-free survival did not differ by RNI receipt (premenopausal hazard ratio [HR], 1.03; P = .87; postmenopausal HR, 0.85; P = .16).
“The incidence of locoregional recurrence observed in this study was reassuringly low” and “disease-free survival was not associated with RNI receipt,” even among women who did not get chemotherapy, the authors conclude. The results inform risk/benefit discussions about RNI, particularly that “omission of chemotherapy is not itself an independent indication for RNI.”
The work was led by Reshma Jagsi, MD, DPhil, of Emory University, Atlanta, Georgia, and published July 6 in JAMA Oncology.
As an observational study, confounding by indication is likely and thus limits the ability to estimate treatment effects. Follow-up was relatively short.
The work was funded by the National Cancer Institute and the Susan G. Komen Foundation. Investigators reported ties to Merck, Eisai, AstraZeneca, Pfizer, and other companies.
For more from Medscape Oncology, join us on Twitter and Facebook
Source: Read Full Article