Magnetic resonance imaging patterns of tumor response to chemotherapy in desmoid‐type fibromatosis

BACKGROUND: We aimed to investigate changes in volume and MRI T2‐weighted intensity in desmoid‐type fibromatosis (DF) receiving methotrexate plus vinca‐alkaloids (MTX‐VA) at Istituto Nazionale dei Tumori, Milan. METHODS: All cases of sporadic DF treated with MTX‐VA from 1999 to 2019 were reviewed. MRIs at baseline, 6 and 12 months of chemotherapy and at treatment withdrawal were retrospectively reviewed, contouring the tumor lesion and measuring diameters, volume, and mean T2‐signal intensity (normalized to muscle) changes. These parameters were also evaluated according to clinical variables. RESULTS: Thirty‐two DF patients were identified. Best RECIST response was: 25% partial response, 69% stable disease, 6% progression. A ≥65% tumor volume reduction was observed in 38%, <65% reduction in 53%, an increase in 9%. 22% had RECIST stable disease with a ≥65% tumor volume reduction. T2‐signal intensity decreased by ≥50% in 47%, <50% in 41% and increased in 12%. In patients with symptomatic improvement while on therapy and in patients maintaining symptomatic improvement during follow‐up, median T2‐signal intensity showed a reduction along the time points (3.0, 1.9, 1.2, 1.1; 2.9, 2.0, 1.2, 1.2, respectively); in patients without symptomatic improvement and in those clinically progressing during follow‐up, a reduction was not observed. High T2‐signal intensity at baseline was observed in patients showing RECIST progression during follow‐up. CONCLUSIONS: In this series, RECIST detected a lower proportion of responses as compared to volumetric and T2‐signal changes. T2‐signal reduction seemed to better reflect symptomatic improvement. High T2‐signal intensity at baseline was related to a higher proportion of further progression.