S317
Clinical - Breast
ESTRO 2026
esophageal dose constraints into breast RT planning, highlighting a rarely explored determinant of treatment tolerability. Keywords: hypofractionation, dysphagia, dermatitis
Digital Poster 4126
Are we ready to omit RNI in NSABP B-51/RTOG 1304 patient cohort? Real world data with longer follow- up duration. SENEM Alanyalı, Mert Delikaya, Fethiye Odacı, Zeynep Ozsaran Radiation Oncology, Ege University, Izmir, Turkey Purpose/Objective: The NSABP B-51/RTOG 1304 randomized trial evaluated the impact of regional nodal Irradiation (RNI) and survival in patients with clinical stage T1–T3, N1, M0 breast cancer who achieved ypN0 status after neoadjuvant chemotherapy (NACT).The results, published in NEJM in June 2025 (1), demonstrated that RNI did not reduce the risk of invasive breast cancer recurrence or death in ypN0 patients. However, given numerous studies showing survival benefits of RNI in initially node-positive patients, concerns arise about rapidly applying the NSABP B-51 results to our clinical practice. Therefore, we aimed to evaluate the recurrence and survival outcomes of the NSABP B-51 RT arm-like cohort in our patient population. Material/Methods: We retrospectively evaluated 95 breast cancer patients treated between 2011 and 2023 with clinical stage T1– T3, N1, M0 who achieved ypN0 status after NACT and received adjuvant RT. SPSS version 24 was used for for descriptive statistics and survival outcomes. Results:
Patient characteristics are summarized in Table 1. Regarding NACT response, 71.6% of patients achieved pathological complete response, while 28.4% had a good or partial response. The median follow-up was 84 months (range: 21–176). Recurrence patterns with NSABPB 51 trial results comparison were listed in table 1. In the NSABP B-51 trial, the median follow-up duration is 59.2 months, and the rate of invasive breast cancer recurrence or breast cancer–related death was reported as 6.5% (50/772), while in our cohort, this rate was 6.3% (6/95), showing similarity. Isolated distant metastasis occurred in 5.2% (5/95) versus 5.3% (41/772) in NSABP B-51; isolated locoregional recurrence was 2.1% (2/95) versus 0.5% (4/772); and simultaneous local plus distant recurrence was 1.1% (1/95) versus 0.3% (2/772). Isolated LRR is higher in our patient population. Characteristics of the eight recurrent cases are presented in Table 2. Among these, 75% (6/8) recurrences occurred within the first three years, while 25% (2/8) were late recurrences ( ≥ 5 years). Conclusion: In our patient population with a median follow-up of 7 years, LRR rates were slightly higher than those in the NSABP B-51 cohort, highlighting the need for longer follow-up in breast cancer studies. It is likely that the LRR rates may also differ at 10 years of follow-up in the NSABP B-51 trial. References: 1. Omitting Regional Nodal Irradiation after Response to Neoadjuvant Chemotherapy, Authors: Eleftherios P. Mamounas, M.D., Hanna Bandos, Ph.D., Julia R. White, M.D., Thomas B. Julian, M.D., Atif J. Khan, M.D., Simona F. Shaitelman, M.D., Mylin A. Torres, M.D., +20 , and Norman Wolmark, M.D.Author Info & AffiliationsPublished June 4, 2025 N Engl J Med 2025;392:2113-2124 DOI: 10.1056/NEJMoa2414859 VOL. 392 NO. 21 Keywords: yp NO, NACT, NSABP B51
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