The role of adjuvant radiotherapy in patients with malignant phyllodes tumor of the breast: a propensity-score matching analysis

Background and objectives Malignant phyllodes tumor of the breast (MPTB) is a kind of rare tumor. Our objective was to investigate the role of adjuvant radiotherapy (RT) in MPTB patients. Methods MPTB patients were identified in the Surveillance, Epidemiology and End Results (SEER) database. KaplanMeier curves and multivariable Cox proportional hazards analyses were conducted to determine the effect of adjuvant RT on MPTB patients. Propensity-score matching (PSM) method was used to balance the clinicopathological characteristics. Results A total of 1353 MPTB patients were included in our study and the median follow-up time was 99 months (range: 0-331 months). 16.7% (226) MPTB patients received adjuvant RT, of which 49.1% (111) received mastectomy and 50.9% (115) underwent breast conservation surgery (BCS). Patients receiving adjuvant RT were more likely to be white, with better differentiation and larger tumors (p < 0.05). Multivariate analysis showed that poorer tumor differentiation grade, larger tumor size, and lymph node metastasis were associated with reduced survival while BCS was a protective factor of diseasespecific survival (DSS) (HR 0.297; 95% CI 0.184-0.480) and overall survival (OS) (HR 0.445; 95% CI 0.321-0.616). After PSM, survival curves showed patients did not achieve an improved OS or DSS from adjuvant RT (p > 0.05). In subgroup analysis, no subgroup benefited from adjuvant RT. Exploratory analysis showed a survival benefit trend from adjuvant RT in patients with tumor larger than 50 mm and undergoing BCS. Conclusions Among MPTB patients, adjuvant RT did not improve OS or DSS. In patients with tumor larger than 50 mm and receiving BCS, a survival benefit trend from adjuvant RT existed.