COMPARISON OF GRADING ACCURACY OF PROSTATE CANCER IN SAMPLES ACQUIRED BY A TARGETED AND SYSTEMIC PROSTATE BIOPSY.

Introduction: All malignancies, including prostate cancer, require accurate diagnosing and staging before making a treatment decision. The introduction of targeted biopsies based on prostate MRI findings has raised prostate biopsy accuracy. Guided biopsies target the tumor itself during the biopsy instead of the most common tumor sites as is the case with a systemic biopsy. Some studies report that targeted biopsies should lower prostate cancer biopsy undergrading and overgrading. Goals: To determine the incidence of prostate cancer biopsy undergrading in patients who underwent a classic systemic biopsy compared to patients who underwent a mpMRI cognitive targeted biopsy. Materials and methods: We identified the patients from our database who underwent a radical prostatectomy at our institution from January 1st, 2021, to June 30th, 2021.There were 112 patients identified. Patients were stratified into two groups based on the type of biopsy that confirmed prostate cancer. The mpMRI (N=50) group had a mpMRI cognitive guided transrectal ultrasound (TRUS) prostate biopsy performed, and the non-mpMRI group (N=62) received a classic, systemic TRUS biopsy. We compared the biopsy results with the final pathological results, and searched for undergrading or overgrading in the biopsies compared to the final histological report. Results: The undergrading was found in 17,7% (N=11) cases in the non-mpMRI group and in 12,0% (N=6) of cases in the mpMRI group (p=0,02, Mann-Whitney U test). No overgrading was found in our cohort. All cases of undergrading had Grade Group 1 in the biopsy report and Grade Group 2 in the final specimen report. The charasteristics of patients are listed in Table 1. Discussion and conclusion: In our cohort, the patients who underwent a mpMRI targeted biopsy had a lower undergrading incidence. During a systemic TRUS biopsy, the urologist targets the areas of the prostate where cancer is most commonly located, which is usually the peripheral zone of the prostate. Since different areas of the tumor have different areas of differentiation, only a low-grade part of the tumor is sometimes biopsied, which results in a sampling error. Once the prostate is removed, the whole tumor is analyzed, so the obtained pathological results related to the removed prostate are far more accurate than the analysis of prostate cores obtained by biopsy.