High Prognostic Value of ¹⁸F-FDG PET for Metastatic Gastroenteropancreatic Neuroendocrine Tumors: A Long-Term Evaluation

Abstract

This study aimed to evaluate the long-term prognostic usefulness of 18 F-FDG PET for patients with metastatic gastroenteropancreatic neuroendocrine tumors (GEPNETs). Methods: Thirty-eight patients with metastatic GEPNETs were prospectively enrolled. Initial check-up comprised CT scan, 111 In-pentetreotide scintigraphy (SRS), and 18 F-FDG PET. Only 18 F-FDG PET-positive lesions with a maximum standardized uptake value (SUV max ) greater than 4.5 or an SUV ratio (SUV max tumor to SUV max nontumoral liver tissue, or T/NT ratio) of 2.5 or greater were considered positive for prognosis-that is, indicating a poor prognosis. Progressionfree survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Factors associated with survival were assessed with univariate and multivariate analyses, using the Cox regression model. Results: Median PFS and OS were significantly higher for patients with a negative 18 F-FDG PET finding, with an OS of 119.5 mo (95% confidence interval [CI], 72-∞), than for patients with a positive 18 F-FDG PET finding (only 15 mo [95% CI, 4-27]) (P , 10 −3 ). Median PFS and OS were significantly higher for the patient group that had a positive SRS than the group with a negative SRS (P 5 0.0002). For patients with a positive SRS, PFS and OS were significantly shorter when the 18 F-FDG PET finding was positive: 19.5 mo (95% CI, 4-37) for PFS and 119.5 mo (95% CI, 81-∞) for OS (P , 10 −3 ). In the patient group with a lowgrade GEPNET and a positive SRS, PFS and OS were also significantly lower for patients with a positive 18 F-FDG PET. At 48-mo follow-up, 100% of patients who had a positive 18 F-FDG PET for disease progression (of which 47% were also SRS-positive) were deceased, and 87% of patients with a negative 18 F-FDG PET were alive (P , 0.0001). The T/NT ratio was the only parameter associated with OS on multivariate analysis. Conclusion: Overall, 18 F-FDG PET appears to be of major importance in the prognostic evaluation of metastatic GEPNET. A positive 18 F-FDG PET with an SUV ratio (T/NT) of 2.5 or greater was a poor prognostic factor, with a 4-y survival rate of 0%. A positive SRS does not eliminate the need for performing 18 F-FDG PET, which is of greater prognostic utility.

Comparison of the Impact of 68Ga-DOTATATE and 18F-FDG PET/CT on Clinical Management in Patients with Neuroendocrine Tumors

“…In their study, SUV max for 68 Ga-DOTANOC correlated with prognosis, whereas that for 18 F-FDG did not. Several reports have indicated that 18 F-FDG positivity is associated with a worse prognosis, although to our knowledge most of these studies did not specifically investigate the role of SUV max (22,38). In our study, we found that metastases demonstrated by either tracer correlated with a shorter survival, with bone metastases correlating with the worst prognosis.…”

Current Concepts in 68Ga-DOTATATE Imaging of Neuroendocrine Neoplasms: Interpretation, Biodistribution, Dosimetry, and Molecular Strategies

“…Vice versa, 68 Ga-SSA PET/CT in cases presenting higher Ki-67 values (.50%), even if positive, will likely not affect management. The added value of 18 F-FDG in welldifferentiated NENs (G1 and G2) is still under debate, and no international consensus has been reached (49)(50)(51)(52)(53).…”

Reply: Modifying the Poor Prognosis Associated with 18F-FDG–Avid NET with Peptide Receptor Chemo-Radionuclide Therapy (PRCRT)

“…This point underlines the better prognostic value of 18 F-FDG than of SRS, with a survival rate of 0% at 4 y in cases of 18 F-FDG positivity, regardless of the SRS results, and 70% for patients with positive SRS results and negative 18 F-FDG results (1).…”

“…We have read with great interest the comments of Hofman et al regarding our recently published study (1) about the high prognostic value of 18 F-FDG PET for metastatic neuroendocrine tumors (NETs). In that prospective study, patients with 18 F-FDG-avid NETs, defined by a standardized uptake value (SUV) exceeding 4.5 or a tumor-to-nontumor SUV ratio (T/NT ratio) exceeding 2.5, had dramatically decreased overall survival (OS) in comparison with patients with 18 F-FDG-negative NETs.…”

“…There is also well-documented evidence that 18 F-FDG PET is a better prognostic indicator than Ki-67 evaluation, as several patients with low (,2%) or intermediate (2%-20%) Ki-67 may exhibit 18 F-FDG avidity and poor prognosis (1,4).…”