While both the Prostate Health Index (phi) and multiparametric magnetic resonance imaging (mpMRI) have demonstrated value for predicting grade reclassification among patients enrolled in active surveillance for prostate cancer, combining the two tools provides greater accuracy than either modality alone, according to research presented at the AUA annual meeting in San Francisco.
Furthermore, the combination appears to be a more powerful predictor of grade reclassification than the combination of mpMRI and PSA density (PSAD), which has been previously shown to be useful in the active surveillance population, Johns Hopkins researchers reported.
The improved predictive performance of combining information from the serum biomarker assay and mpMRI was identified in a retrospective study that included data from 253 men enrolled in the Johns Hopkins Active Surveillance program. The results showed that a cutoff of <25.6 for phi, which encompasses the lowest quartile of scores in the study population, combined with a PI-RADS v2 score ≤3, had a 98% negative predictive value (NPV) for grade reclassification to Gleason score >6 and an area under the curve (AUC) of 0.70.
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Additional calculations determined that the use of both parameters to guide biopsy decisions for men enrolled in active surveillance would avoid nearly 20% of surveillance biopsies at the cost of missing only 2.6% of cases of clinically significant disease, said first author Zeyad Schwen, MD, resident at James Buchanan Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore.
“We have been using phi and mpMRI in the follow-up of men in our active surveillance program. According to our new analysis, the combination of these tools might provide greater accuracy for reducing the number of unnecessary surveillance biopsies while minimizing the risk of missing men who may require active treatment,” said Dr. Schwen, who worked on the study with H. Ballentine Carter, MD, and colleagues.
Men were selected for inclusion in the study if they underwent mpMRI and had a phi test within 6 months of each other and subsequently had systematic biopsy with or without targeted biopsy. All men were categorized as either very-low risk or low-risk according to National Comprehensive Cancer Network Guidelines (NCCN) criteria.
The 253 men had been in active surveillance for a median of 24 months (range, 8 to 52 months). Median PSA, PSA density (PSAD), phi, and phi density (PHID) values for the cohort were 6.2 ng/mL, 0.10 ng/mL2, 32.9, and 0.59, respectively. Of the 253 men, 179 (71%) had a PI-RADs v2 score ≤3.
Thirty-eight men (15%) had grade reclassification on surveillance biopsy. Compared to the group of men without grade reclassification, the men with reclassification had significantly higher median phi, PHID, and PSA density (PSAD) values. The percentages of men with PI-RADS v2 4-5 and who were NCCN low-risk were also significantly greater in the group with grade reclassification.
“Not surprisingly, median PSA did not differ significantly between men who did and did not have grade reclassification, showing the limitations of PSA use in the active surveillance population,” Dr. Schwen told Urology Times.