Pilot study of FLT-PET/CT uptake in ovarian cancer patients with biologic correlates

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Background: New imaging modalities for ovarian cancer disease burden are needed. Positron emission tomography (PET) with [F-18] fluorodeoxyglucose (FDG) has shown promise for early prediction of outcome and response to therapy when compared to CT alone. Recent studies have suggested that 3’-fluoro-3’ [F-18] deoxythymidine (FLT) has a higher specificity than FDG. The objective of this study was to correlate FLT tracer uptake with different in vitro quantitation of cellular proliferation. Methods: Patients with suspected or know ovarian cancer and an elevated Ca 125 were recruited for this trial. These patients were injected with 5 mCi of [F-18]FLT intravenously as a slow bolus. After an uptake period of 60 minutes, patients were scanned for approximately 36 minutes by CT and then PET, and images were co- registered. Standardized uptake values (SUV) of both hot and cold areas were obtained and these lesions were biopsied at the time of surgery. Tissue was divided and used for Ki-67 proliferation index staining to determine mitotic index, RNA isolation for rt-PCR for thymidine kinase-1 (TK1) levels, and grown ex vivo for cell proliferation analysis. Univariate analysis was preformed using the student's t-test. Results: PET positive lesions were found to have a significantly increased mitotic index when compared to control lesions (0.134 vs. 0.004, p<0.001). There were no significant differences in relative TK1 levels or ex vivo cell proliferation ability between PET positive and control lesions in the initial four patients. Conclusions: Increased mitotic index by Ki-67 staining correlates with increased FLT activity by PET scan, but not TK1 levels or DNA content. We will continue to explore this modality as compared to FDG-PET in patients with ovarian cancer.

No significant financial relationships to disclose.