Clinical evaluation of the iXip index to reduce prostate re-biopsies

Prostate biopsy is the gold standard for prostate cancer (PCa) diagnosis, but it's invasive and associated with adverse events. Novel reliable tumor biomarkers and accurate non-invasive tests are required to avoid biopsies. The immune complex PSA-IgM is a new marker for PCa, and it has been included in an algorithm to generate the diagnostic index iXip, which determines the probability of having PCa. In this study we evaluated the ability of iXip to reduce the number of repeat biopsies in patients with a previous negative biopsy and suspicious for PCa.

219 patients referred for prostate rebiopsy were included in the study. Each patient underwent a trans-rectal ultrasound-guided prostate biopsy and prostate volume examination. Blood samples were collected before any prostatic manipulation to determine the serological levels of PSA-IgM and PSA. The iXip index was calculated as previously reported using an online calculator.

iXip values in patients with a positive biopsy were significantly higher than the ones observed in negative patients (p-value = 0.001). Based on iXip values, patients were divided in five risk groups: those with iXip < 0.2 had 0% probability of having PCa. High values of the Gleason score (≥7) were observed mostly in patients with iXip 0.3-0.8.

Our preliminary results show that iXip identifies a sub-group of patients who can safely avoid rebiopsy because they do not have PCa. The index is a promising tool that could reduce the number of unnecessary prostate biopsies and the relative clinical complications and expenses.