ARRS 2022 Abstracts

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E1900. 18F-FDG PET/CT Evaluation of Desmoid Fibromatosis
Authors
  1. Gregory Aird; Mayo Clinic
  2. Nicole Winiarczyk; Mayo Clinic
  3. Anna Beam; Mayo Clinic
  4. Stephen Broski; Mayo Clinic
Objective:
The objective of this study was to characterize the 18F-FDG PET/CT imaging features of desmoid fibromatosis (DF).

Materials and Methods:
All institutional biopsy-proven desmoid tumors with a pre-therapy 18F-FDG PET/CT scan from 2001–2019 were retrospectively reviewed. Multiple PET/CT morphologic and metabolic features were assessed. The electronic medical record was cross referenced for demographic, treatment, and follow-up information.

Results:
There were 34 desmoid tumors in 31 patients (17 women, 14 men, mean age 49.8 ± 20.6 years) included in the study. Lesion locations included mesentery (16/34, 47%), pleura (6/34, 18%), trunk (4/34, 12%), extremities (4/34, 12%), brachial plexus (3/34, 9%), and retroperitoneum (1/34, 3%). The average largest dimension was 6.3 ± 4.9 cm (range 1.8–22.7 cm), and average volume was 308.8 ± 810.6 (range 1.1–4577 cm3). The mean SUVmax was 4.1 ± 2.1 (range 1.4–13.1), SUVmean was 2.4 ± 1.3 (range 1.0–8.9), metabolic tumor volume (MTV) was 151.4 ± 352.3 cm3 (range 1.0–1893.3 cm3), and total lesion glycolysis (TLG) was 295.3 ± 602.5 g (range 2.1–2881.7 g). There were 23/34 (68%) with irregular margins and 11/34 (32%) had well-circumscribed margins. Pleural lesions were more likely to have well-circumscribed margins (5/6) compared to lesions at other sites (6/28), p = 0.008. There were no significant differences in SUVmax, SUVmean, MTV, or TLG between abdominal (16/34, 47%) vs. extra-abdominal (18/34, 53%) location (all p-values > 0.05). There were 33/34 lesions with clinical or imaging follow-up; mean follow-up time was 26.2 ± 28.0 months. There were 7/33 (21%) lesions with recurrence or progression following treatment. There was no difference in SUVmax or SUVmean in patients with and without recurrence/progression (SUVmax: 3.7 ± 0.8 vs. 4.1 ± 2.3, p = 0.67; SUVmean: 2.0 ± 0.4 vs. 2.4 ± 1.5, p = 0.41). MTV, TLG, maximal size, and volume were all greater in patients with recurrence/progression versus those without (MTV: 431.3 ± 684.0 vs. 81.8 ± 153.7 cm3, p = 0.019; TLG: 714.3 ± 1031.3 vs. 193.6 ± 400.9 g, p = 0.043; maximal size 10.2 ± 6.7 vs. 5.4 ± 3.9 cm, p = 0.019; volume: 893.3 ± 1641.5 cm3 vs. 163.1 ± 315.1, p = 0.035). There were 22/34 (65%) lesions with a history of surgery or trauma in the region where the desmoid ultimately developed.

Conclusion:
DF is a locally aggressive deep connective tissue malignancy occurring in the musculoaponeurotic tissues, most commonly the abdominal mesentery, abdominal wall, and extremities. Imaging can play an important role in evaluating the disease extent and assessing response to treatment. Although the imaging features of DF have been characterized using many modalities, the role of 18F-FDG PET/CT in DF has yet to be fully defined, with most of the literature consisting of small series and case reports. This study presents the largest cohort of patients with biopsy-proven DF imaged using 18F-FDG PET/CT to date.