External-beam radiotherapy for pediatric and young adult desmoid tumors

To report long-term outcomes following radiotherapy for desmoid tumors in children and young adults and identify variables impacting local-regional control and treatment complications.

From 1978 to 2008, 30 patients <30 years old were treated with radiotherapy for a pathologically confirmed desmoid tumor. The median age at radiotherapy was 23.7 years old (range, 10.3-29.9). Fifteen patients underwent definitive radiotherapy, 14 received radiotherapy after gross total resection, and 1 received preoperative radiotherapy. Sixteen patients received 1.8 Gy once daily and 14 received 1.2 Gy twice daily. Variables analyzed for prognostic value included gender, age at diagnosis, primary or recurrent presentation, age at radiotherapy, tumor site, tumor size, extent of resection, fractionation schedule, and radiotherapy dose.

The actuarial 15-year overall survival and local-regional control rates were 96% and 55%, respectively. Local-regional control in patients <18 years old at the time of radiotherapy was 20% versus 63% in those 18-30 years old (P = 0.08). Local-regional control rates for tumors receiving ≥ 55 Gy and < 55 Gy were 79% and 30%, respectively (P = 0.02). No other factors had a statistically significant association with local-regional control by univariate analysis. Twelve of 30 patients experienced grade 3-4 complications, including pathologic fractures, impaired range of motion, pain, and in-field skin cancers.

The role of radiotherapy in managing young patients with desmoid tumors remains unclear. Younger patient age is associated with inferior local-regional control following RT. In children and young adults, doses ≥55 Gy were associated with improved tumor control, but also lead to increased risk of complications.