Surgery over radiation: A clear path for malignant phyllodes tumors.

e12576 Background: Malignant phyllodes tumors of the breast are rare fibroepithelial neoplasms with potential for local recurrence and metastasis. While surgical resection remains the primary treatment, the role of adjuvant radiation therapy remains debated. This study revisits the debated role of adjuvant radiotherapy on overall survival (OS) in patients with malignant phyllodes tumors. Methods: We conducted a retrospective cohort study using the SEER Research Plus Database, 17 registries (Nov 2023, Sub 2000-2021), to evaluate the overall survival (OS) of patients with malignant phyllodes tumors in the U.S. between 2000 and 2020. Propensity score matching was used to adjust for potential confounders. Patients with benign or borderline histology and those diagnosed outside the study period were excluded. Two cohorts were analyzed: patients who underwent surgery with radiation therapy (Surg/Rad) and those treated with surgery alone (No Radiation). SEER*Stat software version 9.0.31.0 was used for statistical analysis. Kaplan-Meier survival analysis was used to compare the 60-month OS between the groups. Multivariable Cox proportional hazards regression was performed to determine hazard ratios (HR) with corresponding 95% confidence intervals (CI), adjusting for demographic and clinical variables. Results were evaluated using the log-rank test. Results: A total of 2,143 patients met inclusion criteria, with 427 in the Rad/Surg group and 1,716 in the No Radiation group. The No Radiation group exhibited superior OS compared to the Rad/Surg group (86.8% vs. 80.4%, respectively; p < 0.0001). The adjusted HR for OS in the Rad/Surg group was 2.069 (95% CI 1.174-3.648), indicating significantly lower overall survival compared to the No Radiation group. Conclusions: This SEER-based analysis found that adjuvant radiation therapy doesn’t improve OS in patients with malignant phyllodes tumors aligning with the existing literature. Patients treated with surgery alone demonstrated better survival outcomes, suggesting that surgery alone may be the optimal approach for managing these rare tumors.