Prevalence of multiple cancers and detection of unexpected additional primary malignancies in patients undergoing FDG PET/CT: An initial experience

2227 Objectives: PET/CT with 18F-FDG has proven to be effective in detecting and assessing various types of cancers. Because of genetic make up and common risk factors, patients undergoing PET/CT exams may have had or are at risk for developing multiple cancers. The purpose of this study was to evaluate prevalence of multiple cancers and the frequency of incidental detection of additional primary malignancies in FDG PET/CT examination. Methods: True Whole-Body FDG-PET/CT scans covering from the top of head to the bottom of the feet of 540 patients were reviewed. Images were acquired on a PET/CT scanner (Philips Medical Systems) 60 minutes after an intravenous injection of a weight-adjusted dose of 0.14 mCi/kg FDG with a maximum dose of 14 mCi. Reports were retrospectively reviewed, and a log was kept to record cases of known history of multiple cancers other than the indication for the PET/CT scan. Furthermore, another log was kept to record cases of PET/CT findings of PET-positive lesions suggestive of new unexpected additional primary cancer(s). Past presence of prior multiple cancers and/or the diagnosis of additional unexpected primary malignancies were subsequently assessed using all available clinical and pathologic follow-up information. Results: Of the 540 PET/CT studies, 52 (9.6%) patients had multiple primary cancers besides the primary reason for which the PET/CT scan was ordered. Furthermore, PET/CT incidental findings lead to the detection of unexpected additional primary malignancies in 5/540 (0.93%): two cases of prostate cancer, one case of retroperitoneal seminoma, one case of non-small-cell lung cancer, and one case both of melanoma and lymphoma in the same patient. Conclusions: We conclude that multiple synchronous or metachronous cancers are present in a significant number (at least 10.6%) of patients undergoing PET/CT scanning, including the identification of additional unexpected primary cancers in 0.93%. Therefore, a yearly PET/CT may be helpful in surveillance of patients with cancer.