The utility of 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography in the investigation of patients with disseminated carcinoma of unknown primary origin

Purpose: A retrospective analysis of the use of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) positron emission tomography (PET) was performed in patients with histologically proven disseminated carcinoma of unknown primary tumor (CUP). Procedures: The records of 31 patients with CUP, excluding patients with isolated neck metastases, were reviewed to identify the ability of PET to detect the putative primary site (PPS) and/or to change therapeutic management. Results: In eight out of 31 cases (26%), a PPS was confirmed, either definitively (one pathologically, one radiologically) (true positive) or clinically (six cases). For three cases (10%), histological evidence of a primary tumor distant from the PPS was found (false positive). In a further seven cases (23%), the PPS remained unconfirmed, whereas for 13 cases (42%) no PPS was identified. In five out of seven patients in whom the PET suggested a high probability of having identified the primary site, the PPS was confirmed definitively or clinically. PET altered clinical management in at least 12 cases (38%). Conclusions: PET contributed to the management of previously extensively investigated patients with CUP. Identification of a PPS and/ or change in management was documented in 38% of cases, the majority of which were lung or pancreatic cancer. These findings are worthy of evaluation in a prospective study.