Optimal surgical margin and the efficacy of adjuvant radiotherapy in borderline and malignant phyllodes tumors: a multicenter retrospective study

Abstract

Purpose: Optimal management of borderline and malignant phyllodes tumors (PT) is not well established, especially regarding margin width and the use of adjuvant radiotherapy (RT).This multicenter study aimed to identify prognostic factors and to assess the effectiveness of adjuvant RT. Materials and Methods:We conducted a retrospective analysis of 183 patients (155 surgery-only, 28 adjuvant RT) diagnosed with borderline or malignant PT from 2009 to 2025.To address selection bias, whereby RT is preferentially given to higher-risk patients, we used overlap weighting based on propensity scores, which estimates the average treatment effect in the overlap population (ATO).Independent prognostic factors were identified through multivariable Cox regression with Firth's penalized likelihood.Results: A resection margin <1 mm was identified as the only independent predictor of local recurrence in multivariable analysis (hazard ratio [HR], 2.07; 95% confidence interval [CI], 1.03 to 4.08; p = 0.043).Although conventional analysis did not show a benefit from RT, overlap-weighted analysis suggested an improved local recurrence-free survival with adjuvant RT, though this was not statistically significant (HR, 0.25; 95% CI, 0.05 to 1.19; p = 0.081).Distant metastasis events were rare (n = 3), and no significant difference in distant metastasis-free survival was observed after overlap weighting (HR, 2.27; 95% CI, 0.33 to 15.66; p = 0.404).In an exploratory subgroup analysis, no local recurrence (LR) was observed in the 12 borderline patients who received adjuvant RT (0/12 vs. 27/136 in surgery-only).Conclusion: Margins <1 mm were independently linked to an increased risk of LR.After adjusting for selection bias, adjuvant RT showed a trend toward reduced LR, though it did not achieve statistical significance.Adjuvant RT might be considered for selected high-risk patients.