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. Kaplan-Meier 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 disease-specific 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.
Keywords: Adjuvant radiotherapy; MPTB; PSM; SEER; Survival.