Desmoid fibromatosis: MRI features of response to systemic therapy

Imaging criteria for measuring the response of desmoid fibromatosis to systemic therapy are not well established. We evaluated a series of patients with desmoids who underwent systemic therapy to document magnetic resonance imaging (MRI) features associated with a positive clinical response.

This Institutional Review Board-approved retrospective study included 23 patients (mean age 40.5) with 29 extra-abdominal tumors. Therapeutic regimens included cytotoxic chemotherapy (n = 19), targeted therapy (n = 3), and nonsteroid anti-inflammatory drugs (NSAIDS; n = 1). Clinical effects were categorized as progressive disease, stable, or partial response. Maximum tumor dimension (D_max), approximate tumor volume (V_Tumor), and quantitative tumor T2 hyperintensity and contrast enhancement (relative to muscle) for pre- and post-treatment MRIs were compared.

Three lesions progressed, 5 lesions were stable, whereas 21 showed a clinical response. D_max decreased more in responders (mean −11.0 %) than in stable/progressive lesions (mean −3.6 and 0 % respectively, p = 0.28, ANOVA); by Response Evaluation Criteria in Solid Tumors (RECIST 1.1) 27 out of 29 lesions were “stable,” including the 3 progressive lesions. In responders, V_Tumor change averaged −29.4 %, but −19.2 % and +32.5 % in stable and progressive lesions respectively (p = 0.002, ANOVA); by 3D criteria 14 out of 29 lesions showed a partial response. T2 hyperintensity decreased by 50–54 % in partial response/stable disease, but only by 10 % in progressive lesions (p = 0.049, t test). Changes in contrast enhancement ranged from −23 % to 0 %, but were not statistically significant among response groups (p = 0.37). Change in T2 hyperintensity showed a positive correlation with volumetric change (r = 0.40).

Decreases in volume and T2 hyperintensity reflect the positive response of desmoid fibromatosis to systemic therapy; RECIST 1.1 criteria are not sensitive to clinically determined tumor response.