Single institution experience of split course radiotherapy in patients with desmoid tumors.

Purpose: This study aimed to assess the feasibility of split course radiotherapy (SCRT) and reports long-term outcomes in patients with desmoid tumors (DT). Patients and methods: 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 median dose for the first phase was 3,969 cGy/22 Fx (range: 2,999-4,305 cGy), and 2,495 cGy/14 Fx (range: 1,982-3,039 cGy) for the second phase. Progression-free survival (PFS) in response to radiotherapy was evaluated using the Kaplan-Meier method and compared using the log-rank test. The prognostic factors associated with survival were evaluated by univariate and multivariate analyses. Results: The median age of all patients was 30 years (range, 7-58 years). With a median follow-up of 60.4 months (range, 2-187 months), eight patients experienced disease progression after treatment. The 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). PFS was not significantly influenced by age, gender, surgery, tumor location, RT technology, or RT dose. Radiation-related acute complications occurred in nine (29%) patients after RT, and RT-related long-term complications occurred in three (9.7%) patients. Conclusion: SCRT with an appropriate treatment interval (<100 days) is well tolerated by DT patients with favorable long-term outcomes.