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.