68Ga-pentixafor PET/CT in diagnosis of lymphoma in gastrointestinal tract

Objectives: Physiological uptake and inflammation of the bowels is an important pitfall in diagnosis of lymphoma in gastrointestinal tract with ¹⁸F-FDG PET/CT. ⁶⁸Ga-pentixafor is a recently established nuclear probe targeting the chemokine receptor subtype CXCR4, which is overexpressed in hematopoietic malignancies and some type of solid tumors. The objective of this study is to investigate whether ⁶⁸Ga-pentixafor has an advantage in diagnosis of lymphoma in GI tract.

Methods: A prospective study was performed in 10 patients with complicated bowel disease, in whom GI lymphoma was clinically suspected but endoscopy with biopsy was non-diagnostic. ⁶⁸Ga-pentixafor and ¹⁸F-FDG PET/CT was performed within 3 days. ¹⁸F-FDG PET/CT images were read by 2 experienced nuclear medicine physicians with more than 5-year experience in PET/CT, and reached a consensus on diagnosis with ¹⁸F-FDG PET/CT. All patients were hospitalized and underwent repeated biopsy or surgery with definitive diagnosis.

Results: 6 patients were histologically proved to have GI lymphoma (4 diffuse large B cell lymphoma, 2 T cell lymphoma). Intestinal tuberculosis (1), Behcet’s disease with ileal bladder fistula (1), autoimmune enteropathy (1), and loss of protein bowel disease (1) were diagnosed in the other 4 patients. ⁶⁸Ga-pentixafor showed moderate to high uptake in GI tract lesions in 6/6 patients with GI lymphoma. In 4 patients with benign bowel disease, ⁶⁸Ga-pentixafor did not show increased radioactivity in GI tract. ¹⁸F-FDG PET/CT showed intense and segmental/diffuse radioactivity in the bowels in 9 patients, and no increased uptake in GI tract was noted in 1 patient. In the 6 patients with GI lymphoma, a true positive diagnosis for lymphoma was made in 4 patients with ¹⁸F-FDG PET/CT. In the 2 false negative patients, 1 patient had diffuse FDG uptake in colon and jejunum, which was previously considered to be physiological; the other patient did not have any increased uptake in GI tract. In the 4 patients with benign bowel disease, 2 were true negative for ¹⁸F-FDG PET/CT diagnoses; however, the other 2 patients were mistaken for diagnosis.

Conclusion: ⁶⁸Ga-pentixafor PET/CT might be helpful in differentiation of GI lymphoma in complicated cases.