COMPARISON OF 68GA-PSMA AND 18F-FDG-PET/CT IN THE ASSESSMENT OF DESMOID TUMORS

Introduction/Justification

Recently, the tracer Prostate Specific Membrane Antigen (PSMA), which can be labeled with the radioisotopes 68Ga or 18F, has been commercially introduced. Theoretically, as the name suggests, it is a substance specific to the membrane of prostate cells and prostate cancer. However, several studies have shown that it is also a marker of neoangiogenesis, leading to its uptake in various other neoplasms and benign diseases.

Objectives

This study aims to evaluate the utility of radiolabeled PSMA in detecting desmoid tumors, comparing it to 18F-luorodeoxyglucose (FDG).

Materials and Methods

Three participants with a confirmed diagnosis of desmoid tumor underwent PET/CT examinations with 18F-PSMA and 18F-FDG, with a maximum interval of 3 days between examinations. Images were visually compared lesion by lesion and the maximum standardized uptake value (SUV) was calculated for each lesion and each radiopharmaceutical.

Results

All lesions presented uptake of both 68Ga-PSMA and 18F-FDG. In the first patient, 3 lesions were identified: a mass adjacent to the pancreas measuring 5.4 cm (FDG: SUV = 2.0) (PSMA: SUV = 8.2), a mass in the right iliac fossa measuring 7.7 cm (FDG: SUV = 3.8) (PSMA: SUV = 5.7), and another involving the duodenojejunal transition measuring 4.1 cm (FDG: SUV = 1.9) (PSMA: SUV = 3.7). In the second patient, a mass was identified adjacent to the head and uncinate process of the pancreas measuring 9.2 cm (FDG: SUV = 9.8) (PSMA: SUV = 6.1). In the third patient, an irregular retroperitoneal mass was identified at the level of the aortic bifurcation (FDG: SUV = 2.3) (PSMA: SUV = 2.4).

Conclusion

Desmoid tumors can demonstrate uptake of both 68Ga-PSMA and 18F-FDG. The intensity of tracer uptake in the lesions is variable, with some showing greater uptake of FDG, others of PSMA, suggesting a potential complementary role for these radiotracers in desmoid tumors.