Diffusion tensor imaging (DTI) of desmoid tumours in familial adenomatous polyposis: initial experience

To assess the feasibility of diffusion tensor imaging (DTI) of desmoid tumours in familial adenomatous polyposis (FAP).

Following ethical approval and informed consent, FAP patients with desmoids underwent DTI. Fractional anisotropy (FA), relative anisotropy (RA) and apparent diffusion coefficient (ADC) were compared to control muscle using Mann-Whitney test; and to tumour site and signal intensity using one way analysis of variance (ANOVA). Imaging was repeated after 1 year.

15 desmoids (6 intra-abdominal; 6 abdominal wall, 3 extra-abdominal; size range: 1.6-22.9 cm) were evaluated in 9 patients. DTI was successful in 12/15 desmoid tumours. Median (range) of RA, FA and ADC were 0.23×10(-3) mm2/s (0.17-0.26); 0.27×10(-3) mm2/s (0.21-0.31); and 1.65×10(-3) mm2/s (1.39-1.91) for desmoids, significantly different from muscle: 0.27×10(-3) mm2/s (0.23-0.40), 0.32×10(-3) mm2/s (0.28-0.46), and 1.45×10(-3) mm2/s (0.92-1.63) (p=0.0001, p=0.0001, p=0.0016, respectively). There was no difference in RA, FA or ADC between tumour sites, or signal intensity (p>0.05). One year later, 2 patients had died. Tumour increased in size in 1 patient (+61%). DTI quantification was possible in only 8/13 tumours. FA, RA and ADC were not significantly different from baseline (p=0.77, 0.71 and 0.34, respectively).

Assessment of water diffusion has the potential to provide insight into tumour microstructure and is feasible in desmoids. Desmoid tumours demonstrate anisotropy but diffusion is less restricted and less directional than in muscle.