Adding PSMA PET/CT imaging to mpMRI improves detection of significant prostate cancer

A retrospective analysis published in the Journal of Urology showed that adding ⁶⁸Ga-PSMA PET/CT diagnostic imagingmpMRI improved the detection of significant prostate cancer and enhanced the capacity to identify appropriate patients for active surveillance.¹

“If our results are confirmed in prospective studies, then this could potentially translate to increased diagnostic yield at prostate biopsy and decreased number of negative prostate biopsy procedures,” wrote the study authors, led by John Yaxley, MBBS, FRACS, associate professor at the University of Queensland in Australia.

Overall, the study included 1123 men with prostate cancer who had received an mpMRI and ⁶⁸Ga-PSMA PET/CT imaging before undergoing robot assisted laparoscopic radical prostatectomy (RALP). The median PSA was 6 and the median Gleason score (GS) on biopsy and RALP histology was 4+3.

The investigators collected tumor locations from both mpMRI and ⁶⁸Ga-PSMA PET/CT and compared these to embedded prostate histology. “Lowest apparent diffusion coefficient value on mpMRI and the highest maximum standardized uptake value (SUVmax) on ⁶⁸Ga-PSMA PET/CT were collected on the index lesions to perform analysis on detection rates,” the authors wrote.

The results showed that compared to RALP histology, there was not a statistical difference between mpMRI and ⁶⁸Ga-PSMA PET/CT in detecting tumor foci, at 963 versus 987, respectively (P = .10). There was also not a significant difference between the imaging modalities in detecting index lesions at 888 versus 914, respectively (P = .11).

Overall, imaging with ⁶⁸Ga-PSMA PET/CT detected tumors in 117 (10%) men that mpMRI did not identify; similarly, imaging with mpMRI detected tumors in 93 (8%) men that were not identified by ⁶⁸Ga-PSMA PET/CT.

Index GS ≥3+4 tumors were seen on mpMRI and ⁶⁸Ga-PSMA PET/CT in 80% (881/1106) and 82% (905/1106) of men, respectively. “Importantly, when combining both mpMRI and ⁶⁸Ga-PSMA PET/CT, the index GS ≥3+4 cancer was identified in 92% (1020/1106) of men,” the author wrote, noting that compared to the accuracy of using either mpMRI or ⁶⁸Ga-PSMA PET/CT alone, there was a statistically significant enhancement in accuracy when combining the imaging modalities.

The authors also noted, “Only 10% of patients with Gleason score ≤3+4 on biopsy with an SUVmax <5 were upgraded to ≥4+3 on RALP histology, compared to 90% if the SUVmax was >11.”

In their concluding remarks the authors wrote, “Combining mpMRI and ⁶⁸Ga-PSMA PET/CT in a primary diagnostic setting could better identify where to target on biopsy, increasing the diagnostic yield, improving concordance with underlying tumor grade and therefore improving management recommendations. In contrast, a combination of a negative mpMRI and negative ⁶⁸Ga-PSMA PET/CT would likely suggest a low risk of a clinically significant prostate cancer. The triage of this group away from biopsy to serial PSA monitoring could decrease the number of negative biopsies.”

Reference

1. Raveenthiran S, Yaxley WJ, Franklin T, et al. Findings in 1123 men with pre-operative 68Ga-PSMA PET/CT and mpMRI compared to totally embedded radical prostatectomy histopathology. Implications for the diagnosis and management of prostate cancer [published online ahead of print October 25, 2021]. J Urol. doi: 10.1097/JU.0000000000002293.