Can fluorodihydroxyphenylalanine PET replace somatostatin receptor scintigraphy in patients with digestive endocrine tumors?

Abstract

The aim of this study was to evaluate whether (18)F-fluorodihydroxyphenylalanine ((18)F-FDOPA) PET is accurate for the diagnosis and follow-up of any type of well-differentiated digestive endocrine tumor and to assess its performance compared with standard somatostatin receptor scintigraphy (SRS) using (111)In-pentetreotide. We reviewed the results of 33 evaluable (18)F-FDOPA PET and (111)In-pentetreotide SRS examinations performed between March 2002 and September 2005 in 30 patients referred for documented well-differentiated digestive endocrine tumor. The sensitivity and accuracy of (18)F-FDOPA PET were significantly better for carcinoid tumors (defined according to the World Health Organization 2000 classification) (n = 19) than for noncarcinoid tumors (n = 14)-that is, 93% versus 25% for sensitivity (P < 0.01) and 89% versus 36% for accuracy (P < 0.01), respectively. In contrast, the performances of (111)In-pentetreotide SRS did not differ according to the carcinoid or noncarcinoid type of the primary endocrine tumor-that is, 81% versus 75% for sensitivity and 79% versus 71% for accuracy, respectively. In carcinoid tumors, comparison between (18)F-FDOPA PET and (111)In-pentetreotide SRS showed that (18)F-FDOPA PET more accurately evaluated the extent of disease than (111)In-pentetreotide SRS. (111)In-Pentetreotide SRS did not reveal any additional lesions in any case. Conversely, in noncarcinoid tumors, the extent of the disease was more accurately evaluated in all cases by (111)In-pentetreotide SRS than by (18)F-FDOPA PET. This preliminary study emphasizes the importance of a precise histologic characterization of well-differentiated digestive endocrine tumor to select the best radiopharmaceutical. (18)F-FDOPA PET appears to be useful in carcinoid tumors and could become the first-line scintigraphic imaging modality for these tumors, but (111)In-pentetreotide SRS appeared to be a better first-line scintigraphic imaging modality for noncarcinoid digestive tumors.