Study: Pre-prostatectomy MRI can identify patients with high recurrence risk

A retrospective study recently published in the American Journal of Roentgenology suggested that pre-operative MRI findings may have comparable predictive efficacy to post-prostatectomy pathologic staging in assessing the risk of biochemical recurrence (BCR) of prostate cancer (PCa).¹

“For patients with MRI-visible extraprostatic extension and seminal vesicle invasion, the ability to identify increased risk of BCR preoperatively provides the opportunity to consider neo-adjuvant or early adjuvant therapies and may help predict outcomes in patients undergoing non-surgical therapies or surveillance,” the authors wrote.

For the study, researchers assessed findings of extraprostatic extension (EPE) and seminal vesicle invasion (SVI) on preoperative MRI and postoperative pathologic staging in predicting BCR in 604 patients (median age of 60) who had prostate MRI prior to having a radical prostatectomy (RP).

The study authors found that EPE on pre-op MRI was associated with a 3.6 hazard ratio (HR) for BCR of PCa in comparison to 5.0 hazard ratio for EPE on RP pathology. For MRI-detected EPE, the researchers noted a three-year BCR-free survival (RFS) rate of 59 percent (versus 84 percent for those without EPE) in comparison to 58 percent for EPE on post-op RP pathology (versus 89 percent for those without EPE).

Seminal vesicle invasion on MRI had a 4.4 HR for BCR of PCa in comparison to a 4.6 HR for SVI on RP pathology, according to the researchers. They added that the three-year BCR-free survival rates for SVI were 50 percent with pre-op MRI detection (versus 80 percent for those without SVI) and 54 percent with post-op RP pathology (versus 83 percent for those without SVI).

“For patients with MRI-visible EPE and SVI, the ability to identify increased risk of BCR preoperatively provides the opportunity to consider neo-adjuvant or early adjuvant therapies and may help predict outcomes in patients undergoing non-surgical therapies or surveillance,” wrote study co-author Baris Turkbey, MD, a senior clinician and radiologist affiliated with the Molecular Imaging Branch of the National Cancer Institute and National Institutes of Health (NIH) in Bethesda, Md.

In a subset of 374 patients with Gleason score grading from biopsy and RP pathology, the researchers utilized the University of California San Francisco (UCSF)-Cancer of the Prostate Risk Assessment (CAPRA) model to predict BCR of PCa. They found that the only CAPRA-based models to reveal significantly different RFS rates between low-risk and medium-risk groups were the CAPRA-MRI models.

“The CAPRA-MRI models were likewise the only models for which both intermediate- and high-risk groups demonstrated significantly greater BCR risk compared to the low-risk group,” noted Turkbey and colleagues. “The findings support incorporation of MRI findings into BCR prediction models to help inform decisions before RP about post-RP monitoring and therapy, and even the decision to undergo RP.”

Beyond the inherent limitations of a retrospective single-center study, the researchers noted that changes in MRI protocols, including the advent of high b-value diffusion-weighted imaging, and clinical management of localized prostate cancer occurred during the 10-year study period. Factors limiting broader extrapolation of the study results included the use of an endorectal coil for MRI exams and interpretation of all MRIs being completed by one genitourinary radiologist. The study authors also suggested that BCR rates may be underestimated due to a limited median follow-up of two years for patients without BCR.

Reference

1. Merriman KM, Harmon SA, Belue MJ, et al. Comparison of MRI-Based Staging and Pathologic Staging for Predicting Biochemical Recurrence of Prostate Cancer After Radical Prostatectomy [published online ahead of print July 5, 2023]. Am J Roentgenol. doi: 10.2214/AJR.23.29609.