Paraneoplastic syndromes: detection of malignant tumors using [(18)F]FDG-PET.

Aim: Paraneoplastic syndromes (PS) comprise a variety of clinical symptoms and diseases associated with underlying malignancy. Differentiation towards benign autoimmune diseases is necessary due to different therapeutic options. This diagnostic challenge includes cost- and time-consuming methods and is not successful in many cases. The aim of this study was the evaluation of [(18)F]fluorodeoxyglucose positron emission tomography ([(18)F]FDG-PET) for detecting or ruling out malignancy in these patients.

Methods: In this retrospective work-up a total of 30 patients with suspected PS (m:f = 17:13, mean age 55, range 22-76 years) were examined with [(18)F]FDG-PET between 1996 and 2001. Diagnoses were erythrodermia, cerebellar degeneration, dermatomyositis, polyneuropathia and others. PET scans were compared to histopathological (n=14), radiological and follow up data (mean follow up 3.6 years, range 1-6 years).

Results: In 7 out of 30 patients (23%) an underlying malignancy was detected. Six out of 7 malignant neoplasms showed a distinctly increased glucose consumption. One benign neoplasm caused increased tracer uptake, another PET positive patient refused biopsy and showed no growth of a malignant tumour during clinical follow up of 28 months. The remaining 21 patients without suspicious glucose consumption did not demonstrate a malignancy in other diagnostic modalities or during subsequent clinical follow-up.

Conclusion: [(18)F]FDG-PET seems to be a useful tool in the diagnostic work-up of patients with suspected paraneoplastic syndrome.