The enigma of myxofibrosarcoma of the extremity

BACKGROUND: The reported high rate of local recurrence (LR) in myxofibrosarcoma raises the question of whether this sarcoma histology should be considered radioresistant. In this study, the authors compared rates and patterns of LR of high-grade (HG) myxofibrosarcoma with rates and patterns of HG leiomyosarcoma, which was chosen because of the similarity in incidence and general treatment approach. METHODS: Two hundred two patients with primary, nonmetastatic extremity myxofibrosarcoma (n = 114) and leiomyosarcoma (n 88) underwent limb- sparing surgery and were followed prospectively. All 202 patients had HG tumors, and 138 patients (68%) received adjuvant radiation therapy. RESULTS: The groups were comparable in terms of age, sex, and receipt of chemotherapy. Compared with leiomyosarcoma, myxofibrosarcoma presented more frequently with tumors > 5 cm (P <.001), deep location (P.036), and upper extremity site (P=.015). In addition, rates of positive/close margins (P <.001) and the receipt of radiation therapy (P <.001) were significantly higher in the myxofibrosarcoma group. The 5- year overall LR rate was not significantly different according to histology (14.6% for myxofibrosarcoma, 13.2% for leiomyosarcoma; P=.594). The only predictor of LR for the whole cohort of patients was positive/close margins (P=.01). Of 17 myxofibrosarcoma LRs, 8 (47%) occurred out of field, versus 1 of 12 (8%) leiomyosarcoma LRs (P.04). Leiomyosarcoma more commonly recurred distantly (54.1% vs 24.3% at 5 years; P.014). CONCLUSIONS: Despite more adverse clinical features, myxofibrosarcoma recurred distantly less often than leiomyosarcoma, whereas the LR rates were comparable between the 2 groups, suggesting that adjuvant radiation therapy is effective in myxofibrosarcoma. Myxofibrosarcoma LRs more commonly occurred out of field. Reduction in radiation field margins may not be advisable in patients with myxofibrosarcoma. Cancer 2012; 118: 518- 27. (C) 2011 American Cancer Society.