Role of Gallium-68 DOTATOC PET-CT in Neuroendocrine Tumors with Unknown Primary Site

Objectives Previous studies suggest a survival advantage in patients (pts) with metastatic neuroendocrine tumor (NET), who undergo resection of the primary tumor. The goal of this study is to evaluate Ga-68 DOTATOC PET-CT in localization of the primary NET in pts presenting with metastases and unknown primary site.

Methods A single center prospective study was performed to evaluate the safety and efficacy of Ga-68 DOTATOC PET-CT in pts with proven or suspected NET. Ga-68 DOTATOC was produced under a physician-sponsored investigational new drug (IND) approval using an automated 68Ge/68Ga generator coupled with a ModularLab PharmTracer fluid handling system (Eckert-Ziegler). PET-CT scans were obtained approximately 60 min after the IV administration of 148 MBq of Ga-68 DOTATOC with a low-dose non-contrast CT. Images were interpreted qualitatively with focal uptake above normal background considered positive for NET.

Results 36 pts with metastatic NET and unknown primary tumor site were evaluated with Ga-68 DOTATOC PET-CT. No primary tumor was identified in 7 pts, who did not have DOTATOC avid metastases. In 29 pts with DOTATOC avid metastases, Ga-68 DOTATOC PET-CT suggested a primary tumor site in 19 pts. The primary site indicated by Ga-68 DOTATOC PET-CT was confirmed in 11 pts, by histology in 8 and by imaging in 3 pts. There were 3 false positives, either nontumoral or lymphadenopathy suggesting primary tumor. 5 lesions identified on Ga-68 DOTATOC PET-CT scans remain unconfirmed. 7 pts underwent resection of primary tumor and 1 pt underwent peptide receptor radionuclide therapy, resulting in a major change in management in 28% of pts, who have DOTATOC avid metastases and unknown primary tumor site.

Conclusions Ga-68 DOTATOC PET-CT can identify the primary tumor, which leads to a significant change in management in pts with metastatic NET and unknown primary tumor site.