Breast
S1007 adds locoregional context to Oncotype-guided de-escalation: low LRR risk in favorable-biology N1 regardless of RNI receipt.
SWOG S1007 (RNI/LRR secondary analysis)
5-yr LRR 0.55-0.85% with/without RNI after BCS; IDFS not associated with RNI in HR+/HER2- N1 favorable-biology breast cancer.
vs leading data
- vs MA.20 / EORTC 22922: both showed RNI improved DFS in unselected N1, but predated Oncotype-guided systemic de-escalation; S1007 population is biologically lower-risk
7 details
ForHR+/HER2-, Oncotype RS ≤25, N1 (1-3 nodes) breast cancer, BCS or mastectomy
- 📊 5-yr cumulative LRR by locoregional treatment
Treatment 5-yr LRR BCS + RT with RNI 0.85% BCS + RT without RNI 0.55% Mastectomy + PMRT 0.11% Mastectomy, no RT 1.7% - 📐 IDFS by RNI receipt — no significant association in either menopausal group
- Premenopausal: HR 1.03 (95% CI 0.74-1.43), p=0.87
- Postmenopausal: HR 0.85 (95% CI 0.68-1.07), p=0.16
- 🔍 Secondary analysis of S1007 (N=4871): HR+/HER2-, Oncotype RS ≤25, 1-3 nodes; endocrine ± chemo; RT data prospectively collected
- 🔍 59% of RT recipients received RNI; median f/u 6.1 yrs
- ⚠️ RT allocation was NOT randomized — practice-pattern data; clinicians likely selectively added RNI to higher-risk pts within this already favorable-biology group
- ⚠️ IDFS analyses landmarked at 1 yr and adjusted for menopause, RS, tumor size, nodes, surgery — but residual confounding cannot be excluded
- 📊 Chemo omission (in endocrine-only arm) was not independently associated with higher LRR — Oncotype-based systemic de-escalation appears locoregionally safe here
Open questions
- Would a randomized RNI omission trial confirm safety in Oncotype-selected N1?
- Do pts with 3 nodes warrant RNI even at low recurrence score?
📚 Sources · 📄 1 paper
Radiotherapy Use and Incidence of Locoregional Recurrence in Patients With Favorable-Risk, Node-Positive Breast Cancer Enrolled in the SWOG S1007 Trial.
Abstract
IMPORTANCE: Little is known about regional nodal irradiation (RNI) practice patterns or rates of locoregional recurrence (LRR) with and without RNI in patients with limited nodal disease and favorable biology treated with modern surgical and systemic therapy, including approaches that de-escalate those latter treatments.<br/><br/>OBJECTIVE: To investigate how often patients with low-recurrence score breast cancer with 1 to 3 nodes involved receive RNI, incidence and predictors of LRR, and associations between locoregional therapy and disease-free survival.<br/><br/>DESIGN, SETTING, AND PARTICIPANTS: In this secondary analysis of the SWOG S1007 trial, patients with hormone receptor-positive, ERBB2-negative breast cancer, and a Oncotype DX 21-gene Breast Recurrence Score assay result of no more than 25, were randomized to endocrine therapy alone vs chemotherapy then endocrine therapy. Prospectively collected radiotherapy information was collected from 4871 patients treated in diverse settings. Data were analyzed June 2022 to April 2023.<br/><br/>EXPOSURE: Receipt of RNI (targeting at least the supraclavicular region).<br/><br/>MAIN OUTCOME(S) AND MEASURE(S): Cumulative incidence of LRR was calculated by locoregional treatment received. Analyses were assessed for associations between invasive disease-free survival (IDFS) and locoregional therapy, adjusted for menopausal status, treatment group, recurrence score, tumor size, nodes involved, and axillary surgery. Radiotherapy information was recorded in the first year after randomization, so survival analyses were landmarked as starting at 1 year among those still at risk.<br/><br/>RESULTS: Of 4871 female patients (median [range] age, 57 [18-87] years) with radiotherapy forms, 3947 (81.0%) reported radiotherapy receipt. Of 3852 patients who received radiotherapy and had complete information on targets, 2274 (59.0%) received RNI. With a median follow-up of 6.1 years, the cumulative incidence of LRR by 5 years was 0.85% among patients who received breast-conserving surgery and radiotherapy with RNI; 0.55% after breast-conserving surgery with radiotherapy without RNI; 0.11% after mastectomy with postmastectomy radiotherapy; and 1.7% after mastectomy without radiotherapy. Similarly low LRR was observed within the group assigned to endocrine therapy without chemotherapy. The rate of IDFS did not differ by RNI receipt (premenopausal: hazard ratio [HR], 1.03; 95% CI, 0.74-1.43; P = .87; postmenopausal: HR, 0.85; 95% CI, 0.68-1.07; P = .16).<br/><br/>CONCLUSIONS AND RELEVANCE: In this secondary analysis of a clinical trial, RNI use was divided in the setting of biologically favorable N1 disease, and rates of LRR were low even in patients who did not receive RNI. Disease-free survival was not associated with RNI receipt; omission of chemotherapy among patients similar to those enrolled in the S1007 trial is not an independent indication for use of RNI.