Adjuvant radiotherapy and survival in patients with malignant phyllode tumors: a population-based retrospective study

To assess whether adjuvant radiotherapy (RT) confers a survival benefit in patients with malignant phyllodes tumors of the breast (MPTB).

We conducted a retrospective cohort study of 1899 adult MPTB patients in the SEER database. Patients were categorized as having received RT (341) and not having received RT (1558). Baseline demographic data, tumor grade, AJCC stage, surgery approach, chemotherapy, and local lymphatic biopsy were extracted. Breast cancer-specific survival (BCSS) and overall survival (OS) of MPTB patients before and after propensity score matching (PSM) were compared using Kaplan-Meyer analysis. Predictors of RT were studied using multifactorial logistic regression. Multivariate Cox proportional risk regression was used to calculate hazard ratio (HR) and 95% confidence interval (CI) for outcome-related factors. Subgroup analyses explored effect modification by grade, stage, and surgery.

Multifactorial logistic regression showed that year of diagnosis, tumor grade, surgical approach and adjuvant chemotherapy were significant predictors of RT. Kaplan-Meier analysis showed that BCSS and OS were worse in the RT group before PSM (both p < 0.001), and there was no significant difference between the two groups after PSM (both p > 0.05). In a multifactorial Cox model, RT was not associated with BCSS (HR 0.975; 95% CI 0.699-1.36; p = 0.881) and OS (HR 0.867; 95% CI 0.662-1.135; p = 0.299) in MPTB patients. Classification of MPTB patients by tumor grade, AJCC.T, AJCC.N, and surgical approach did not identify subgroups that would benefit from long-term survival outcomes (BCSS or OS) from RT (all p > 0.05).

In this large retrospective cohort of MPTB patients, adjuvant RT was not associated with improved long-term survival-even among those with high-risk features. Prospective studies are needed to further clarify its therapeutic value.