PHI to Predict Upgrading of Prostate Cancer Patients on 5ARI

New Orleans—Low-risk prostate cancer patients eligible for active surveillance may not be accurately identified via a single transrectal biopsy (TRUS); resampling is often recommended for more accurate classification. Results of recent studies have suggested that the Beckman Coulter Prostate Health Index (PHI) is a significant predictor of high-grade prostate cancer, defined as Gleason score of greater than seven. However, according to E. David Crawford, MD, and colleagues, those studies did not include patients on 5-alpha reductase inhibitors (5ARI).

The researchers conducted a pilot study to determine whether PHI predicts upgrading and upstaging on resampling for men on 5ARI. They reported study results during a session at the AUS 2015 Annual Meeting.

Following an initial negative TRUS or detection of low-risk cancer, 47 patients elected template-guided transperineal mapping biopsy (TPMB). In an effort to reduce prostate size, all patients had 5ARI prior to TPMB. Hybritech calibration from serum samples drawn prior to TPMB were used to measure prostate specific antigen (PSA), free PSA, and p2PSA. The researchers calculated percent free PSA as free PSA/PSA ´ 100 and PHI = (p2PSA/free PSA) ´ &[root](PSA).

Patients were upgraded when Gleason scores increased by one or more from TRUS to TPMB. Patients were upstaged if unilateral on TRUS changed to bilateral in TPMB or the increase in the number of positives cores was three or more from TRUS to TPMB.

Odds ratio (OR) and statistical significance, defined as ≥.05, were determined by Wilcoxon rank sum and logistic regression analysis (LRA). Receiver operating curve (ROC) analysis was done to compare performance of PHI.

The mean age of study participants was 64 years, the mean PSA was 7.4 ng mL-1, the percent p2PSA was 6,32%, and PHI was 37. Of the 47 patients, 24 had both positive and 4 had both negative TRUS and TPMB. Eleven patients had positive TRUS and negative TPMB; eight patients had negative TRUS and positive TPMB.

Fifteen of the 47 patients were upgraded. PHI (6.32 vs 28.21; P=.0029) predicted upgrading. In the LRA, PHI (OR, 1,1; P=.01) also predicted patients upgraded. In the ROC analysis, there were no differences in area under the curve for PHI (0.77), PSA (0.68), and percent free PSA (0.71).

Furthermore, 25 of the 47 patients were upstaged by PHI (median 45.33 vs 24.54 P=.001). PHI (OR, 1.1; P=.0018) also predicted upstaging in the LRA. Area under the curve of PHI (0.82) was significantly different than area under the curve of PSA (0.64; P=.025), but not area under the curve of percent free PSA (0.65).

The researchers cited the relative small sample size as a possible study limitation.

“Our study demonstrates the potential clinical utility of PHI for identification of high risk prostate cancer patients on 5ARI. Patients with high PHI who have favorable features on TRUS may choose TPMB before electing surveillance or watchful-waiting,” the researchers said.

Source: Crawford ED, Arangua P, Jones C, et al. Prostate health index predicts upgrading of men on 5-alpha reductase inhibitors. Abstract of a presentation at the American Urological Association 2015 Annual Meeting, New Orleans, Louisiana, May 15, 2015.