Prospective Comparison of mpMRI and 18F-FMAU PET/CT in Image-Guided Prostate Biopsy for Detection of Cancer: Preliminary Results

Introduction: We aimed to evaluate the potential complementary utility of PET with the cellular proliferation biomarker, [18F]-2’-fluoro-5-methyl-1-beta-D-arabinofuranosyluracil (18F-FMAU), in localization of sites for image-guided biopsy in men with suspected prostate cancer.

Methods: 17 men with suspected prostate cancer scheduled to undergo standard transrectal ultrasound (TRUS) guided prostate gland biopsy were prospectively recruited in this Instituitional Review Board approved investigation. Patients underwent standard of care mpMRI and consented to have additional investigational PET/CT performed 60 min after intravenous injection of 10 mCi 18F-FMAU. PIRADS v2.1 scores of 3 and higher on mpMRI and visually discernable focal radiotracer localization higher than background prostate uptake level were considered for biopsy. PET/CT and mpMRI were fused with TRUS images for real-time hybrid image-based targeting of biopsy needle in addition to standard 12-core biopsy. All harvested biopsy tissues were examined for presence of tumor. If imaging was positive in a sextant region, this finding was considered true positive if the biopsy was positive for presence of tumor regardless of whether the tissue was obtained through standard grid or image-guidance in that same sextant region.

Results: Tissue samples obtained from 20 image-guided biopsies were examined histologically: 9 benign, 6 Gleason Score (GS) 3+3 (ISUP grade 1), and 5 GS 3+4 (ISUP grade 2), with range of biopsy core tumor involvement of 5%-50% and tumor length of 1-10 mm. For ISUP grade 1, 18F-FMAU PET/CT was TP in 3, and FN in 3, while mpMRI was TP in 1 and FN in 4. For ISUP grade 2, 18F-FMAU PET/CT was TP in 3, and FP in 2, while mpMRI was 5 TP. Findings of mpMRI and 18F-FMAU PET/CT were concordant in 10 (both imaging modalities TP in 3, TN in 1, FP in 4, and FN in 2) and discordant in 10. Overall, mpMRI resulted in 6 TP, 4 TN, 5 FP, and 5 FN. 18F-FMAU PET/CT findings were 6 TP, 2 TN, 9 FP, and 3 FN. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for detection of prostate cancer were 54.5%, 44.4%, 54.5%, 44.4%, and 50% for mpMRI, and 66.6%, 18.2%, 40%, 40%, and 40% for 18F-FMAU PET/CT, respectively.

Conclusions: 18F-FMAU PET/CT may complement mpMRI by enhancing sensitivity in detecting prostate cancer. Further post-hoc quantitative data analysis will be performed to optimize the PET image evaluation scheme for improving the diagnostic performance in localizing candidate sites for image-guided biopsy in men with suspected prostate cancer.

Supported by grants R21-EB017568 and P30-CA014089 from the U.S. National Institutes of Health.