Mesenchymal chondrosarcoma (MCS) is a distinct, very rare sarcoma with little evidence supporting treatment recommendations.

Specialist centres collaborated to report prognostic factors and outcome for 113 patients.

Median age was 30 years (range: 11–80), male/female ratio 1.1. Primary sites were extremities (40%), trunk (47%) and head and neck (13%), 41 arising primarily in soft tissue. Seventeen patients had metastases at diagnosis. Mean follow-up was 14.9 years (range: 1–34), median overall survival (OS) 17 years (95% confidence interval (CI): 10.3–28.6). Ninety-five of 96 patients with localised disease underwent surgery, 54 additionally received combination chemotherapy. Sixty-five of 95 patients are alive and 45 progression-free (5 local recurrence, 34 distant metastases, 11 combined). Median progression-free survival (PFS) and OS were 7 (95% CI: 3.03–10.96) and 20 (95% CI: 12.63–27.36) years respectively. Chemotherapy administration in patients with localised disease was associated with reduced risk of recurrence (P = 0.046; hazard ratio (HR) = 0.482 95% CI: 0.213–0.996) and death (P = 0.004; HR = 0.445 95% CI: 0.256–0.774). Clear resection margins predicted less frequent local recurrence (2% versus 27%; P = 0.002). Primary site and origin did not influence survival. The absence of metastases at diagnosis was associated with a significantly better outcome (P < 0.0001). Data on radiotherapy indications, dose and fractionation were insufficiently complete, to allow comment of its impact on outcomes. Median OS for patients with metastases at presentation was 3 years (95% CI: 0–4.25).

Prognosis in MCS varies considerably. Metastatic disease at diagnosis has the strongest impact on survival. Complete resection and adjuvant chemotherapy should be considered as standard of care for localised disease.