Impact of Metastasis Surgery and Alkylating-Agent-Based Chemotherapy on Outcomes of Metastatic Malignant Phyllodes Tumors: A Multicenter Retrospective Study

Background Metastatic phyllodes tumors have poor prognosis with median overall survival of 11.5 months. The objective of this study is to identify prognostic factors and the best options for management of metastatic malignant phyllode tumors (MMPTs). Patients and Methods A multicentric retrospective study, including cases of MMPT from 10 sarcoma centers, was conducted. The primary end-point was overall survival (OS), and the secondary end-point was the clinical benefit of chemotherapy (CBCT) rate. Results 51 MMPT patients were included. Median time from diagnosis to metastatic recurrence was 13 months. Management of MMPT consisted in surgery of the metastatic disease for 16 patients (31.3%), radiation therapy of the metastatic disease for 15 patients (31.9%), and chemotherapy for 37 patients (72.5%). Median follow-up was 62.1 months [95% confidence interval (CI) 31-80 months]. Median OS was 11.5 months (95% CI 7.5-18.7 months). On multivariate analysis, two or more metastatic sites [hazard ratio (HR) 2.81, 95% CI 1.27-6.19; p = 0.01] and surgery of metastasis (HR 0.33, 95% CI 0.14-0.78; p = 0.01) were independently associated with OS. The CBCT rate was 31.4% and 16.7% for the first and second lines. Polychemotherapy was not superior to single-agent therapy. Alkylating-agent-based chemotherapy, possibly associated with anthracyclines, was associated with a better CBCT rate than anthracyclines alone (p = 0.049). Conclusions The results of this study emphasize the impact of the number of metastatic sites on survival of MMPT patients and the leading role of metastasis surgery in MMPT management. If systemic therapy is used, it should include alkylating agents, which are associated with a better clinical benefit.