2718 - Re-Evaluating the Role of Post-Mastectomy Radiation Therapy for Node-Negative Breast Cancer in the Modern Therapy Era: A Matched Cohort Analysis of SUPREMO Trial
Presenter(s)
Y. Chu1, X. Wang2, and J. Ma2; 1Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, Shanghai, China, 2Department of Radiation Oncology, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University; Shanghai Clinical Research Center for Radiation Oncology; Shanghai Key Laboratory of Radiation Oncology, Shanghai, China
Purpose/Objective(s):
Post-mastectomy radiation therapy (PMRT) is not routinely recommended for patients with T1-2, node-negative (N0) breast cancer due to the overall low rates of locoregional recurrence (LRR). The EORTC 22922/10925 trial showed that elective regional nodal irradiation in stage I–III disease reduced breast cancer recurrence and breast-cancer-specific mortality at long-term follow-up, although overall survival (OS) benefits were modest or not consistently significant. In contrast, the SUPREMO trial, focusing on intermediate-risk post-mastectomy patients, demonstrated that chest wall irradiation did not improve 10-year OS, disease-free survival (DFS), or distant metastasis-free survival (DMFS), and only minimally reduced chest wall recurrences. The indication of PMRT in this specific population remains a subject of ongoing clinical investigation and is not yet clearly defined in current guidelines. To further investigate this paradigm, we applied the SUPREMO trial criteria to a contemporary cohort of node-negative patients and evaluated their long-term outcomes.Materials/Methods: We retrospectively analyzed 2098 consecutive female patients with pT1–2N0 breast cancer who underwent curative surgery between January 2005 and December 2014. Among these, 338 patients met the eligibility criteria of the SUPREMO trial. Clinicopathologic characteristics, treatment details, and follow-up data were systematically collected. Primary endpoints included disease-free survival (DFS), local recurrence-free survival (LRFS), locoregional recurrence–free survival (LRRFS), distant metastasis–free survival (DMFS), and overall survival (OS).
Results:
The SUPREMO-matched cohort demonstrated high 8-year survival: LRRFS 95.5%, LRFS97.8%, DMFS 89.5%, DFS 87.9%, and OS 91.1%. In the overall cohort, non-RNI patients achieved 97.5% 8-year and 96.8% 10-year LRRFS,98.6% 8-year and 98.0 10-year LRFS, 94.1% 8-year and 92.9 10-year DMFS, 93.2% 8-year and 91.6 10-year DFS, 95.4% 8-year and 92.7 10-year OS. Multivariate analysis confirmed tumor size >2 cm and tumor location in the medial/center as independent LRRFS risk factors (both P<0.05).This finding is consistent with the univariate analysis. Although high-risk patients (1-2 factors) had significantly lower LRRFS than low-risk patients (0 factors), their absolute outcomes remained favorable (97.0% at 8 years and 96.2% at 10 years).Conclusion: Patients with pT1–2N0 breast cancer receiving modern systemic therapy have excellent survival and low locoregional recurrence rates, both in the SUPREMO-matched cohort and overall. Despite higher risks associated with larger tumors and located in the medial/center, absolute recurrence rates remain low, suggesting that routine RNI can be safely omitted in these patients.