Local aggressiveness and prognostic prediction in desmoid-type fibromatosis: insights from ¹⁸F-FDG PET/CT

To investigate the value of ¹⁸F-FDG PET/CT in assessing the local aggressiveness of desmoid-type fibromatosis (DF) and in predicting prognosis of DF.

We retrospectively analyzed ¹⁸F-FDG PET/CT of DF lesions in participants. Clinical data and ¹⁸F-FDG PET/CT imaging features were collected and analyzed. The diagnostic performance of ¹⁸F-FDG PET/CT versus contrast-enhanced MRI (CE-MRI) for assessing peritumoral invasion was compared using reference of pathology. Lesions were followed up to record progressive disease (PD) and postoperative recurrence (POR), and event-free survival (EFS) was determined. Univariate and multivariate Cox regression analyses were performed to identify independent predictors of PD or POR.

Fifty-five lesions from 44 participants were included. ¹⁸F-FDG PET/CT showed higher accuracy and sensitivity than CE-MRI for assessing peritumoral invasion, with no statistically significant differences in paired comparisons. Notably, pathology in one case demonstrated tumor invasion of the lymph node capsules. Furthermore, DF lesions with PD or POR had significantly higher maximum standardized uptake value (SUV_max) and target-to-background ratio (TBR). SUV_max, TBR and irregular lesion morphology were identified as independent predictors of PD or POR. The AUC for SUV_max was 0.79 (95% CI: 0.64-0.95), with sensitivity, specificity, and overall accuracy of 78.6% (11/14), 82.9% (34/41), and 81.8% (45/55), respectively. Kaplan-Meier survival analysis revealed that SUV_max> 5.0 was associated with significantly shorter EFS (692.4 [427.5-957.3] days vs. 2419.9 [1989.5-2850.3] days).

¹⁸F-FDG PET/CT showed numerically higher sensitivity and accuracy than CE-MRI for assessing peritumoral invasion of DF lesions, though with lower specificity. SUV_max, TBR, and lesion morphology were independent predictors of PD or POR.