UCSF

Purpose

To develop techniques and establish a workflow using hyperpolarized carbon-13 (¹³ C) MRI and the pyruvate-to-lactate conversion rate (k_PL ) biomarker to guide MR-transrectal ultrasound fusion prostate biopsies.

Methods

The integrated multiparametric MRI (mpMRI) exam consisted of a 1-min hyperpolarized ¹³ C-pyruvate EPI acquisition added to a conventional prostate mpMRI exam. Maps of k_PL values were calculated, uploaded to a picture archiving and communication system and targeting platform, and displayed as color overlays on T₂ -weighted anatomic images. Abdominal radiologists identified ¹³ C research biopsy targets based on the general recommendation of focal lesions with k_PL  >0.02(s^-1 ), and created a targeting report for each study. Urologists conducted transrectal ultrasound-guided MR fusion biopsies, including the standard ¹ H-mpMRI targets as well as 12-14 core systematic biopsies informed by the research ¹³ C-k_PL targets. All biopsy results were included in the final pathology report and calculated toward clinical risk.

Results

This study demonstrated the safety and technical feasibility of integrating hyperpolarized ¹³ C metabolic targeting into routine ¹ H-mpMRI and transrectal ultrasound fusion biopsy workflows, evaluated via 5 men (median age 71 years, prostate-specific antigen 8.4 ng/mL, Cancer of the Prostate Risk Assessment score 2) on active surveillance undergoing integrated scan and subsequent biopsies. No adverse event was reported. Median turnaround time was less than 3 days from scan to ¹³ C-k_PL targeting, and scan-to-biopsy time was 2 weeks. Median number of ¹³ C targets was 1 (range: 1-2) per patient, measuring 1.0 cm (range: 0.6-1.9) in diameter, with a median k_PL of 0.0319 s^-1 (range: 0.0198-0.0410).

Conclusions

This proof-of-concept work demonstrated the safety and feasibility of integrating hyperpolarized ¹³ C MR biomarkers to the standard mpMRI workflow to guide MR-transrectal ultrasound fusion biopsies.