Role of F-18-FDG PET/CT in follow-up of patients with treated leiomyosarcoma

Objectives Leiomyosarcoma is a relatively uncommon malignancy. In this study, we evaluated the utility of PET/CT in management of patients with previously treated leiomyosarcoma.

Methods 19 pts, 13 females, 6 males, aged 25 - 75 years old, with history of excised leimyosarcoma (13 high grade, 6 low grade) were included. Whole body scan was obtained within 60- 90 minutes after IV administration of 555-777 MBq F-18-FDG. Both low dose CT-attenuated and non-attenuated PET images were evaluated. Presence of abnormal increased FDG activity and abnormal CT findings were noted. Imaging results were compared with histopathological examinations and final clinical outcome.

Results 19 pts had 29 studies, 18 for re-staging after excision and 11 for treatment response evaluation. 47 lesion sites were evaluated: PET and CT were concordant in 40 lesions: 29 TP, 9 TN, and 2 FP. Both were FP in a case of metastasis to the liver capsule with no hepatic involvement and in a postsurgical bed. The two imaging technique were discordant in 7 lesion sites. In 3 sites, PET was TN while CT was FP: retroperitoneal lymph nodes, benign peritoneal fluid, and posterior aortocaval mass. PET was TP while CT was FN in mesenteric and bony metastases. PET was FP in 2 cases of post-surgical and degenerative changes. In the lesions with increased FDG uptake, SUV max was significantly higher (p= <0.016) in high grade leiomyosarcoma (range 3.0 - 25.7, average 8.2, median 6.0) than low grade tumors (range 2.9 - 7.4, average 4.5, median 3.8). Imaging results:

Conclusions With no false negative PET study noted, PET/CT imaging is useful for management of patients with previously treated leiomyosarcoma even in those with low-grade tumor type. SUV max is significantly higher in high grade tumors

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Imaging Results in 47 Lesions