18F-FDG PET-CT in the evaluation of paraneoplastic syndromes: experience at a regional oncology centre.

OBJECTIVES

Paraneoplastic syndromes (PNS) are remote manifestations of malignancy unrelated to tumour invasion or metastases. They pose a diagnostic challenge because of diverse presentations. (18)F-Fluorodeoxyglucose ((18)F-FDG) PET-CT is an emerging technique for the detection of malignancy; however, there is a paucity of data with regard to its role in the evaluation of PNS and its relation to pretest clinical risk.

METHODS

A retrospective review of the database at the West of Scotland PET centre from 2007 to 2010 was conducted. Data extracted included demographics, clinical and pathological diagnosis, presence of classical syndromes, cross-sectional imaging, PET-CT imaging and management changes. A clinical scoring system was constructed to evaluate the pretest likelihood of having PNS, and the impact of a subsequent positive PET-CT scan was evaluated.

RESULTS

A total of 68 consecutive patients with a median age (range) of 58 (23-82) years, of whom 44 (65%) were female, were included. Symptoms were neurological in 55 (81%), musculoskeletal in five (7%), endocrine in three (4%) and constitutional in five (7%) patients. Forty-three (62%) patients had a classical paraneoplastic syndrome and 34 (50%) had positive biomarkers. Eighteen (26%) patients had a positive PET-CT result. PET-CT was concordant with the clinical scoring in 49 (72%) patients; it upgraded the score in eight (12%) patients, and downgraded the score in 11 (16%) patients. Eight (12%) patients had confirmed malignancy. PET-CT was estimated to have 100% sensitivity, 82% specificity, 42% positive predictive value and 100% negative predictive value.

CONCLUSION

PET-CT is a highly sensitive and specific imaging technique in the evaluation of PNS and adds confidence to clinical likelihood.