Characterization of suspicious prostate lesions at multiparametric MRI with dynamic 68 Ga-Gozetotide PET/CT.

Abstract

Background: Prostate cancer (PCa) will affect approximately 12% of US men in their lifetime and remains the 2nd most common cause of cancer-specific death. However, there is a broad spectrum of severity of PCa; some require aggressive treatment and others can "watch-and-wait". Distinction of clinically significant prostate cancer (csPCa) from indolent PCA with current imaging methods remains challenging.

Objective: This study aims to evaluate dynamic prostate specific membrane antigen (PSMA) positron emission tomography (PET/CT) in the characterization of suspicious prostate lesions identified on multiparametric MRI (mpMRI).

Methods: Prospective study of biopsy-naïve patients with at least one Prostate Imaging and Reporting Data System (PI-RADS) score 5 or one PI-RADS score 4 plus a prostate specific antigen (PSA) ≥ 10 ng/mL. Dynamic PET/CT was performed for 30 min after administration of ⁶⁸Ga Gozetide. Time activity curves (TAC; kBq/cc) of suspicious prostate lesions were generated. TAC logarithmic slope was calculated for each GG at 5-, 10-, 15-, and 30 min. Apparent diffusion coefficient (ADC) at mpMRI for each lesion was tabulated.

Results: 19 PI-RADS v2.1 ≥ 4 and 6 secondary PI-RADS v2.1 ≥ 3 lesions in 19 patients were analyzed: 4 (16.0%) grade group (GG) 0 (benign), 3 (12.0%) GG 1, 6 (24.0%) GG 2, 6 (24.0%) GG 3, and 6 (24.0%) GG ≥ 4. Significant differences in slope values were observed between clinically insignificant disease (GG 0/1) and GG 2 or higher as early as 5 min post-injection (p < 0.05). At 30 min, GG 1 had the lowest mean slope (- 0.18 ± 0.57) and GG ≥ 4 exhibited the highest mean slope (2.35 ± 2.03). Slope value/ADC ratio further improved discrimination between different GGs.

Conclusions: Dynamic ⁶⁸ Ga Gozetotide time activity curves could distinguish GG0/1 from GG3 and GG4/5 PCa. The addition of mpMRI characteristics could further distinguish GG2 from GG4/5. GG2 could not be distinguished from GG3, probably due to small sample size.

Clinical implications: Dynamic ⁶⁸ Ga Gozetotide PET/CT imaging may offer enhanced discrimination of MRI-visible prostate cancer lesions and assist in management decisions. Study registered with the FDA (IND 144,177) and clinicaltrials.gov (NCT04179968).