Low-grade fibromyxoid sarcoma and sclerosing epithelioid fibrosarcoma, outcome of advanced disease: retrospective study from the Ultra-Rare Sarcoma Working Group

Abstract

Low-grade fibromyxoid sarcoma; Sclerosing epithelioid fibrosarcoma; Systemic therapies

Sarcoma fibromixoide de bajo grado; Fibrosarcoma epitelioide esclerosante; Terapias sistémicas

Sarcoma fibromixoide de baix grau; Fibrosarcoma epitelioide esclerosant; Teràpies sistèmiques

Background To present findings from a retrospective study conducted by the Ultra-Rare Sarcoma Working Group on metastatic low-grade fibromyxoid sarcoma (LGFMS), sclerosing epithelioid fibrosarcoma (SEF), and hybrid (H)-LGFMS/SEF across 28 global centres. Methods Patients treated at participating institutions from January 2000 to September 2022 were retrospectively selected. Diagnosis was confirmed by expert pathologists. Primary endpoint was progression-free survival (PFS-1) from metastasis detection to first progression or death. PFS-2 was calculated from therapy initiation. Results A total of 101 patients were identified (32 LGFMS, 50 SEF, 19 H-LGFMS/SEF). Median (m) follow-up was 62.1 months. mPFS-1 was 28.7, 11.8, and 20.3 months for LGFMS, SEF, and H-LGFMS/SEF, respectively. mOS was 145.8, 41.9, and 113.5 months, respectively. Treatments included anthracycline-based chemotherapy, gemcitabine-based chemotherapy (G), pazopanib, trabectedin, others. mPFS-2 was: 20.1, 5.5, and 3.5 months in H-LGFMS/SEF, SEF, and LGFMS, respectively, with anthracyclines; 19.5, 7.7, and 6.9 months in LGFMS, SEF, and H-LGFMS/SEF, respectively, with pazopanib; 12.0, 9.7, and 3.1 months in H-LGFMS/SEF, LGFMS, and SEF, respectively. Occasional responses occurred with ifosfamide/oral cyclophosphamide, and prolonged stable disease with immune checkpoint inhibitors. Conclusions In this series, the largest available, metastatic LGFMS, SEF, and H-LGFMS/SEF showed different courses. Systemic agents have modest efficacy, informing future trials of novel agents for these tumours.

This work was supported by the Italian Ministry of Health, Ricerca Corrente (no grant number).