Predictive Value of 18F-FDG PET and Somatostatin Receptor Scintigraphy in Patients with Metastatic Endocrine Tumors

The treatment of metastatic neuroendocrine tumors depends on the aggressiveness of the disease. We wanted to know whether F-18-FDG PET and somatostatin receptor scintigraphy (SRS) can predict early disease progression and patient survival. Methods: We undertook a prospective study of patients with metastatic neuroendocrine tumor diagnosed between September 2003 and January 2006. After obtaining signed informed consent from the patients, we performed CT, SRS, and F-18-FDG PET and reviewed histologic data. CT was repeated every 3mo to assess the risk of early progressive disease (first 6 mo), progression- free survival, and overall survival. Results: Thirty-eight patients (mean age, 60 +/- 15 y) were included. Histologically, 4 patients had a high-grade and 34 a low-grade tumor. The results of F-18-FDG PET and SRS were positive in 15 and 27 patients. The 2-y overall survival and progression-free survival were 73% and 45%; 16 patients had early progressive disease. Most F-18-FDG PET-positive patients had early progressive disease (14/15, vs. 2/23 F-18-FDG PET-negative patients), and most SRS-negative patients had early progressive disease (9/11, vs. 7/27 SRS-positive patients); F-18-FDG PET gave excellent negative and positive predictive values of 91% and 93%; F-18-FDG PET results correlated with progression-free survival (P < 0.001) and overall survival (P < 0.001) even when only low-grade tumors were considered. SRS was associated with progression-free survival (P < 0.001) and overall survival (P < 0.03). At multivariate analysis, only F-18-FDG PET was predictive of progression-free survival. Conclusion: F-18-FDG PET exhibits excellent predictive values for early tumor progression. F-18-FDG PET and SRS results correlate with progression-free survival and overall survival even for histologically low-grade tumors. These explorations could be included in the initial work-up for metastatic neuroendocrine tumor.