Lack of Prognostic Value of CTNNB1 Mutation Profile in Desmoid-Type Fibromatosis

Abstract Purpose: This prospective nationwide cohort study aimed to investigate desmoid-type fibromatosis (DF) outcomes, focusing on the prognostic value of CTNNB1 mutations. Experimental Design: ALTITUDES (NCT02867033) was a nationwide prospective cohort study of DF diagnosed between January 2016 and December 2020. At diagnosis, CTNNB1 molecular alterations were identified using next-generation sequencing or Sanger sequencing. The primary endpoint was event-free survival (EFS; progression, relapse, or death). We enrolled 628 patients managed by active surveillance, surgical resection, or systemic treatment as first-line therapy. Results: Overall, 516 (82.2%) patients [368 females (71.3%), median age 40.3 years (range, 1–89)] were eligible for analysis. In 435 (84.3%) cases, there was one CTNNB1 molecular alteration: p.T41A, p.S45F, or p.S45P. The first-line management was active surveillance in 352 (68.2%), surgical resection in 120 (23.3%), and systemic treatments in 44 (8.5%) patients. CTNNB1 mutation distribution was similar across the three therapeutic groups. The median follow-up period was 24.7 (range, 0.4–59.7) months. The estimated 3-year EFS rate was 66.2% [95% confidence interval (CI), 60.5%–71.2%]. DF harboring p.S45F was significantly associated with male sex (P = 0.03), non-abdominal wall sites (P = 0.05), pain (P = 0.007), and large tumor size (P = 0.025). CTNNB1 p.S45F mutation was not significantly associated with EFS, either in univariate (HR, 1.06; 95% CI, 0.65–1.73; P = 0.81) or in multivariate analysis (HR, 0.91; 95% CI, 0.55–1.49; P = 0.71). Conclusions: We found that CTNNB1 mutation profile was associated with unfavorable prognostic factors but was not a prognostic factor for EFS. See related commentary by Greene and Van Tine, p. 3911