Desmoid type fibromatosis in pediatric and young adults from French databases: Clinical characteristics and initial outcome according to age

BackgroundDesmoid type fibromatosis (DTF) are rare intermediate malignancies with unpredictable outcome. Series containing children and young adults (YA) are lacking.MethodsThe aim of this retrospective study was to describe the French population of patients<40 years with DTF diagnosed between 2006 and 2017.ResultsEighty-three children and 881 YA (18–39 years) were included (sex ratio M/F 1.3 and 0.25, respectively). Locations were abdominal wall (40.8%), trunk (23.5 %), extremities (19 %), mesentery (13.5 %) and head and neck (HN) (3.2 %).Tumors were larger in children (7 vs 5.5 cm for YA, p < 0.001), and more frequently located in the abdomen and mesentery in YA (p < 0.001). Patients with Familial Adenomatous Polyposis condition (5.3 % of the cases) were three times more frequent in the multifocal DTF group, and in mesenteric primary (p < 0.001).First-line strategy for 548 patients was: surgery (289 patients), active surveillance (AS, 189 patients), medical treatment (57 patients), other local treatment (radio/cryotherapy, 7 patients), or the combination of several active treatments (6 patients).The 2-year progression free survival (PFS) rate for the whole cohort was 68.3 %, better for YA (69.2 %) than for children (59.5 %, p = 0.0106). Among 548 informative patients, AS was associated with a better PFS (HR = 0.558) and the only variables associated with worse PFS in multivariate analysis were tumor size ≥ 5 cm (HR = 1.785) and location in the extremities (HR = 1.934) or trunk (HR=1.598).ConclusionsClinical DTF presentation is more aggressive in children than YA. AS seems to be a valid first-line option preventing overtreatment, and local progression is linked to size and location, regardless of age.