Researchers have confirmed that the prostate cancer gene 3 (PCA3) is a valid predictor for current cancer and future biopsy outcomes.
"These results confirm that PCA3 can be used in combination with other clinical information to help guide prostate biopsy decisions," say Sheila Aubin (Gen-Probe Incorporated, San Diego, California, USA) and team.
The results are particularly important as they come from the REDUCE trial, a major phase 3 study including four times as many participants as prior studies of PCA3 in men with previous negative biopsy and moderately increased prostate specific antigen (PSA), explains the team.
As reported in the Journal of Urology, the team calculated PCA3 scores from urine samples provided before year 2 and year 4 biopsies performed in 1072 men from the placebo arm of the trial. Men included in the trial had moderately increased levels of PSA (2.5-10.0 ng/mL in those aged <60 years and 3-10 ng/mL in those aged ≥60 years) and a negative biopsy at baseline.
The researchers report that the median PCA3 scores at year 2 and year 4 were 15.9 and 18.0, respectively.
Men with a negative biopsy at both visits displayed median PCA3 values of 15.3 and 16.9 at years 2 and 4, respectively. Among those who had a prostate cancer diagnosed on biopsy, the median PCA3 score was 33.8, compared with a score of 16.7 for those with a negative biopsy.
For the 190 cancers detected, PCA3 scores correlated with biopsy Gleason score. Those with a Gleason score of 6 or less had a median PCA3 score of 31.8, compared with a score of 49.5 among those with a Gleason score greater than 6.
Receiver operating characteristic analysis showed that PCA3 had an area under the receiving operating characteristic curve (AUC) of 0.693, significantly greater than the AUC of 0.612 with serum PSA.
In multivariate regression analysis, a PCA3 level of 35 or more was associated with a significant 2.65-fold increased risk for a positive diagnosis on biopsy, after adjustment for serum PSA, percentage free PSA, age, family history, and prostate volume.
"All traditional variables were strong and independent variables associated with biopsy outcome," note the researchers, "yet the power of PCA3 was not markedly attenuated."
"This finding suggests that PCA3 is a predictor for the clinical management of patients at risk for [prostate cancer]."
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