Systemic treatment in advanced phyllodes tumor of the breast: a multi-institutional European retrospective case-series analyses

Background: We aimed at investigating outcome of systemic treatments in advanced breast PT. Methods: All cases of advanced breast PT treated with systemic treatments from 1999 to 2019, in one of the referral sarcoma centers involved in the study, were retrospectively reviewed. Results: 56 female patients were identified. Median age was 52 (range of 25–76) years. Patients received a median number of 2 systemic treatments (range of 1–4). Best responses according to RECIST were 1 (3.7%) CR, 11 (40.7%) PR, 6 (22.2%) SD, 9 (33.3%) PD with anthracyclines plus ifosfamide (AI); 2 (16.7%) PR, 4 (33.3%) SD, 6 (50.0%) PD with anthracycline alone; 3 (18.8%) PR, 4 (25.0%) SD, 9 (56.3%) PD with high-dose ifosfamide given as a continuous infusion (HD-IFX); 3 (20.0%) SD, 12 (80.0%) PD with a gemcitabine-based regimen (with 2 patients not evaluable); 1 (8.3%) PR, 2 (16.7%) SD, 9 (75.0%) PD with trabectedin (with 1 patient not evaluable); 1 (16.7%) PR, 1 (16.7%) SD, 4 (66.7%) PD with tyrosine-kinase inhibitors (TKI). The median PFS were 5.7 (IQR 2.5–9.1) months with AI; 3.2 (IQR 2.2–5.0) months with anthracycline alone; 3.4 (IQR 1.4–6.7) months with HD-IFX; 2.1 (IQR 1.4–5.2) months with gemcitabine-based chemotherapy; 1.8 (IQR 0.7–6.6) months with trabectedin; 3.4 (IQR 3.1–3.8) months with TKI. With a median follow-up of 35.3 (IQR 17.6–66.9) months, OS from the start of first-line systemic treatment was 15.2 (IQR 7.6–39.6) months. Conclusion: In this series of advanced PT (to our knowledge, the largest reported so far), AI was associated with a high rate of responses, however, with a median PFS of 5.7 months. Other systemic treatments were poorly active.