PURPOSE: With the aim of developing a noninvasive test to detect clinically significant prostate cancer we investigated the potential of capturing cells from urine by microfiltration coupled with analysis of DNA methylation biomarkers.
MATERIALS AND METHODS: In this prospective study urine from men suspected of having prostate cancer who were scheduled for transrectal ultrasound guided biopsy of the prostate was collected before digital rectal examination in 99, after digital rectal examination in 58 and from a urethral catheter in 7. Cells were isolated from whole volume voided urine using a filtration device containing a membrane filter with a pore size of 8 μm. Ten additional men provided 4 or 5 urine cell samples by self-collection prior to biopsy. Cellular DNA was analyzed for 5 methylation biomarkers using ddPCR™ (droplet digital polymerase chain reaction).
RESULTS: Prostate cancer was diagnosed in 117 patients (71%). Across all tumor grades the sensitivity of urine DNA testing was 81% and 60% in samples obtained before and after digital rectal examination, respectively. In a prediction model including prostate specific antigen, patient age and the result of urine DNA analysis to detect high grade disease (Gleason score 7 or greater) an AUC of 0.95 (95% CI 0.90-1.00) was obtained for post-digital rectal examination samples. Analysis of repeat samples demonstrated substantial intraindividual variation in the shedding of cancerous cells in urine.
CONCLUSIONS: Capturing cells from urine by microfiltration provides a novel tool to detect prostate cancer noninvasively with high sensitivity for high grade disease. Repeat sampling may increase sensitivity, particularly when urine is obtained without prior physical manipulation of the prostate.