In a secondary analysis from the SWOG S1007 trial reported in JAMA Oncology, Reshma Jagsi, MD, DPhil, and colleagues found low rates of locoregional recurrence irrespective of the use of regional nodal irradiation in patients with favorable-risk, node-positive breast cancer receiving radiation therapy.
In the trial, patients with hormone receptor–positive, HER2-negative breast cancer and an Oncotype DX 21-gene Breast Recurrence Score ≤ 25 were randomly assigned to receive endocrine therapy alone or chemotherapy followed by endocrine therapy. The current analysis included data from 4,871 patients with one to three involved nodes who were to receive radiotherapy in diverse settings.
Reshma Jagsi, MD, DPhil
Among the 4,871 patients with radiotherapy forms, 3,947 (81.0%) reported receipt of radiotherapy. Among 3,852 patients (79.1%) who received radiotherapy and had complete information on targets, 2,274 (59.0%) received regional nodal irradiation.
Median follow-up was 6.1 years. The 5-year cumulative incidence of locoregional recurrence was 0.85% among patients who received breast-conserving surgery and radiotherapy with regional nodal irradiation; 0.55% among those receiving breast-conserving surgery with radiotherapy without regional nodal irradiation; 0.11% among those receiving mastectomy with postmastectomy radiotherapy; and 1.7% among those receiving mastectomy without radiotherapy. A similarly low cumulative incidence of locoregional recurrence was observed among patients randomly assigned to endocrine therapy without chemotherapy.
Analysis including only regional nodal irradiation receipt and not surgery type showed no significant difference in invasive disease–free survival with regional nodal irradiation receipt vs no receipt of regional nodal irradiation among premenopausal patients (hazard ratio [HR] = 1.03, 95% confidence interval [CI] = 0.74–1.43, P = .87) or postmenopausal patients (HR = 0.85, 95% CI = 0.68–1.07, P = .16).
The investigators concluded, “In this secondary analysis of [SWOG S1007], regional nodal irradiation use was divided in the setting of biologically favorable N1 disease, and rates of locoregional recurrence were low even in patients who did not receive regional nodal irradiation. Disease-free survival was not associated with regional nodal irradiation receipt; omission of chemotherapy among patients similar to those enrolled in the S1007 trial is not an independent indication for use of regional nodal irradiation.”
Dr. Jagsi, of the Department of Radiation Oncology, Winship Cancer Institute of Emory University, is the corresponding author for the JAMA Oncology article.
Disclosure: The study was supported by the National Cancer Institute, Genomic Health, and Susan G. Komen Foundation. For full disclosures of the study authors, visit jamanetwork.com.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.