Extraskeletal Myxoid Chondrosarcoma: Retrospective Case Series Examining Prognostic Factors, Treatment Approaches, and Oncologic Outcomes.

Abstract

Extraskeletal myxoid chondrosarcoma (EMC) is an ultrarare soft tissue sarcoma, and a limited number of studies are published regarding its clinical course and efficacy of treatment. The goal of this retrospective case series is to explore patient characteristics, treatment approaches, and oncologic outcomes to help inform future EMC management. All patients with a diagnosis of EMC seen at the University of Michigan Sarcoma Center between 1998 and 2021 were identified. A chart review was performed to analyze demographics, tumor characteristics, treatments, and outcomes. Forty-four patients with EMC were identified. The median follow-up was 49.8 months. The median age at diagnosis was 57 (range: 25 to 79), and 35 patients (80%) were male. Thirty-four patients (77%) had locoregional disease at diagnosis, and 26 patients (59%) ultimately developed metastatic disease. After locoregional curative-intent surgery, 15 patients had documented recurrence, of which 11 were metastatic (73%). Five-year overall survival was 79% for all patients, 86% for locoregional disease, and 58% for metastatic disease; for locoregional disease, 5-year disease-free and metastasis-free survival post-surgery were 43% and 53%, respectively; 1-year progression-free survival for metastatic disease from the start of first-line systemic therapy was 43%. Older age was the only factor statistically associated with improved prognosis, although perioperative radiotherapy, lower histologic grade, and negative margins also had directional associations with outcomes. The data in this patient series are generally consistent with published literature on EMC and demonstrate a high recurrence rate, high propensity for metastasis, and high rate of progression of metastatic disease on systemic therapy.