Localization of Unknown Primary Site with Ga-DOTATOC PET/CT in Patients with Metastatic Neuroendocrine Tumor.

Localization of the site of the unknown primary tumor is critical for surgical treatment of patients presenting with neuroendocrine tumor (NET) with metastases. Forty patients with metastatic NET and unknown primary site underwent Ga-DOTATOC PET/CT in a single-site prospective study. The Ga-DOTATOC PET/CT was considered true-positive if the positive primary site was confirmed by histology or follow-up imaging. The scan was considered false-positive if no primary lesion was found corresponding to the Ga-DOTATOC-positive site. All negative scans for primary tumor were considered false-negative. A scan was classified unconfirmed if Ga-DOTATOC PET/CT suggested a primary, however, no histology was obtained and imaging follow-up was not confirmatory. The true-positive, false-positive, false-negative, and unconfirmed rates for unknown primary tumor were 38%, 7%, 50%, and 5%, respectively. Ga-DOTATOC PET/CT is an effective modality in the localization of unknown primary in patients with metastatic NET.