Long-Term Outcomes for Patients With Desmoid Fibromatosis Treated With Radiation Therapy: A 10-Year Update and Re-evaluation of the Role of Radiation Therapy for Younger Patients

Purpose: To update our experience with long-term outcomes in patients with desmoid fibromatosis treated with radiation therapy (RT) and to characterize factors associated with increased risk of local recurrence. Methods and Materials: We reviewed the records of 209 consecutive patients with desmoid fibromatosis treated with RT, either alone or as combined-modality therapy (CMT) with surgery, at our institution from 1965 to 2015. Results: Median follow-up time was 98 months (range, 1-509 months). The 5- and 10-year local control (LC) was 71% and 69%, respectively. Fifty-nine patients (28%) experienced a local recurrence at a median time of 23 months (interquartile range, 15-38 months). Among all patients, on multivariable analysis, adjusting for anatomic site, size, age, treatment era (>2005 vs ≤2005), treatment approach (RT alone vs CMT), and an interaction between age and treatment, we found only age ≤30 years (hazard ratio [HR], 2.94; P =.005; 95% confidence interval [CI], 1.38-6.27) and large tumor size >10 cm (HR, 2.51; P =.03; 95% CI, 1.09-5.78) to be correlated with poorer LC. Notably, for patients receiving RT alone, the 5-year LC was 43% for patients ≤30 years old versus 75% for >30 years old (P <.001). On multivariable analyses, for patients receiving RT alone, the only factor associated with inferior LC was age ≤30 years (HR, 2.87; P =.001; 95% CI, 1.51-5.47). The same was true for patients treated with CMT; age ≤30 years was the only factor associated with inferior LC (HR, 5.36; P =.01; 95% CI, 1.40-20.58). Conclusions: Among all patients with desmoid fibromatosis, RT is an effective local therapy for tumor control. However, young patients ≤ 30 years have notably high rates of local recurrence regardless of treatment strategy, which requires further study. Treatment decisions should be risk-adapted by large referral centers with multidisciplinary expertise in desmoid management.