Uncertain Benefit of Regional Nodal Irradiation in Low-Risk BC
TOPLINE:
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.
METHODOLOGY:
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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.
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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.
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The secondary analysis assessed locoregional recurrence (LRR) rates with and without RNI over a median follow-up of 6.1 years.
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Among nearly 4000 patients who received radiotherapy, 2274 received RNI.
TAKEAWAY:
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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.
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Similar low recurrence rates were observed among women who omitted chemotherapy and received endocrine therapy alone.
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Invasive disease-free survival did not differ by RNI receipt (premenopausal hazard ratio [HR], 1.03; P = .87; postmenopausal HR, 0.85; P = .16).
IN PRACTICE:
“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.”
SOURCE:
The work was led by Reshma Jagsi, MD, DPhil, of Emory University, Atlanta, Georgia, and published July 6 in JAMA Oncology.
LIMITATIONS:
As an observational study, confounding by indication is likely and thus limits the ability to estimate treatment effects. Follow-up was relatively short.
DISCLOSURES:
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.
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