This study aimed to assess the feasibility of split course radiotherapy (SCRT) and reports long-term outcomes in patients with desmoid tumors (DT). Between 2001 and 2004, 31 patients with recurrent (n=19) or primary large desmoid fibromatosis (≥10 cm) (n=12) who were treated with SCRT were retrospectively analyzed. All patients were treated with two phases of radiotherapy with a median interval time of 99 days (range: 81-122 days) and a median total dose of 6,399 cGy (range: 5,013-7,039 cGy). The progression free survival (PFS) rate at 3 and 5 years for the whole population was 90% and 71.3%, respectively. PFS for patients with split course of <100 days or ≥100 days interval was 100% vs 78.6% at 3 years, and 80.4% vs 62.9% at 5 years, respectively (P=0.189). In multivariate analysis, the radiotherapy (RT) interval time was an independent prognostic factor for PFS (≥100 days vs <100 days, HR 11.544, 95% CI 1.034-128.878, P=0.047). Radiation-related acute complications occurred in nine (29%) patients after RT, and RT-related long-term complications occurred in three (9.7%) patients. SCRT with an appropriate treatment interval (<100 days) is well tolerated by DT patients with favorable long-term outcomes.
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