S332
Clinical - Breast
ESTRO 2026
Purpose/Objective: The safety of omitting postoperative radiotherapy in patients achieving pathological complete response (pCR) after primary systemic therapy (PST) for breast cancer remains uncertain. The ReSTORE (Radiotherapy after Systemic Therapy: Outcomes and Response Evaluation) study aims to investigate the association between RT, pCR, and clinical outcomes. Material/Methods: Patients with stage I–III breast cancer who received PST and mastectomy, with or without postmastectomy radiation therapy (PMRT), were consecutively treated from two institutions between 2017 and 2023. Clinical, demographic and treatment-related variables were collected. Disease-free survival (DFS) was the primary endpoint. Kaplan–Meier survival comparisons and subgroup analyses by RT and pCR status were performed. Ethical approval was obtained. Results: A total of 275 patients were included, with a median follow-up of 82 months (range 16–166). Patient characteristics and treatments details are summarized in Table 1 and Table 2 respectively.Across the overall cohort, the non-PMRT group showed a numerically higher DFS (68 vs. 59 months) (Fig.1), not statistically significant (p=0.095; HR 1.46, 95% CI 0.9–2.3), consistent with a lower baseline stage and risk profile (such as pCR) in this cohort. As expected, patients achieving pCR had significantly improved DFS compared to those without pCR (p=0.005; HR 2.13, 95% CI 1.25–3.60). Among patients received PMRT, those achieving pCR had significantly better DFS than those without pCR (69,6 vs 55 months).Notably, in patients who were initially node-positive and achieved pCR, PMRT was associated with a significant DFS advantage (p=0.01; HR 2.03, 95% CI 1.14–3.6) (Fig.2), despite small sample size. The cumulative locoregional recurrence (LRR) rate for the entire cohort was 5% when all locoregional events were combined. No statistically significant associations with DFS were observed for age, BRCA status, T stage, ER, or HER2 status in this preliminary analysis.
Conclusion: Preliminary results from this two-centre study confirm the favourable prognosis associated with pCR after PST; however, achieving pCR alone may not suffice to justify omission of postoperative RT, particularly in patients initially presenting with node-positive disease. Prospective studies should integrate additional drivers, such as genomic and/or biomarker-driven tools, baseline stage, and nodal burden, to more precisely identify candidates for omission of PMRT. Keywords: PST, PMRT
Digital Poster 4660
Repeat External Beam Radiotherapy for Locoregional Breast Cancer Recurrence: A Systematic Review Jana Nano 1 , Yunrong Shen 2 , Luisa Allwohn 1 , Sophie T. Behzadi 1 , Sophia Kiesl 1 , Sophie Maier 1 , Rebecca Moser 1 , Syeda Hina Zaidi 2 , Ansam Nail Beddor 2 , Roselyn Salomey Amamoo 2 , Rosemond Sussana
Made with FlippingBook - Share PDF online