Does focal incidental (18)F-FDG PET/CT uptake in the prostate have significance?

(18)F-FDG PET/CT is used to characterize many malignancies, but is not recommended for localized prostate cancer. This study explores the value of multi-parametric MRI (mpMRI) in characterizing incidental prostate (18)F-FDG uptake.

Thirty-one patients who underwent (18)F-FDG PET/CT for reasons unrelated to prostate cancer and prostate mpMRI were eligible for this retrospective study. The mpMRI included T2-weighted (T2W), dynamic contrast enhancement (DCE), apparent diffusion coefficient (ADC), and MR spectroscopy (MRS) sequences. Fourteen patients were excluded (n = 8 insufficient histopathology, n = 6 radical prostatectomy before PET), and final analysis included 17 patients. A nuclear medicine physician, blinded to clinicopathologic findings, identified suspicious areas and maximum standardized uptake values (SUVmax) on (18)F-FDG PET/CT. Sector-based imaging findings were correlated with annotated histopathology from whole-mount or MRI/transrectal ultrasound fusion biopsy samples. Positive predictive values (PPVs) were estimated using generalized estimating equations with logit link. Results were evaluated with Kruskal-Wallis and Dunn's multiple comparisons tests.

The PPV of (18)F-FDG PET alone in detecting prostate cancer was 0. 65. Combining (18)F-FDG PET as a base parameter with mpMRI (T2W, DCE, ADC, and MRS) increased the PPV to 0. 82, 0. 83, 0. 83, and 0. 94, respectively. All benign lesions had SUVmax < 6. Malignant lesions had higher SUVmax values that correlated with Gleason scores. There was a significant difference in SUVmax per prostate between the Gleason ≥ 4 + 5 and benign categories (p = 0. 03).

Focal incidental prostate (18)F-FDG uptake has low clinical utility alone, but regions of uptake may harbor high-grade prostate cancer, especially if SUVmax > 6. Using mpMRI to further evaluate incidental (18)F-FDG uptake aids the diagnosis of prostate cancer.

Abdominal imaging. 2015 Aug 04 [Epub ahead of print]

Anna M Brown, Maria L Lindenberg, Sandeep Sankineni, Joanna H Shih, Linda M Johnson, Suneha Pruthy, Karen A Kurdziel, Maria J Merino, Bradford J Wood, Peter A Pinto, Peter L Choyke, Baris Turkbey

Molecular Imaging Program, National Cancer Institute, NIH, 10 Center Drive, Room B3B85, Bethesda, MD, 20892, USA.