Prostate cancer detection rate at second and third biopsy. Predictive factors and risk groups for cancer diagnosis.

OBJECTIVES The diagnosis of prostate cancer is obtained with the performance of a prostate biopsy. Repetition of biopsies is required in patients with negative biopsies when there is high suspicion for cancer. The objective of this study is to know the prostate cancer detection rate in second and third prostatic biopsies and to identify the clinical factors with predictive value for positivity. We also want to establish risk groups for cancer diagnosis after one or two previous negative biopsies. METHODS Retrospective study of patients undergoing a second or third prostatic biopsy. We determined the rate of cancer diagnosis for both. We performed univariate and multivariate analysis (multiple logistic regression) to analyse any relationship between clinical variables (PSA, PSA density, PSA F/T ratio, PSA velocity, digital rectal examination, transrectal ultrasonography, prostate volume, time between biopsies, pathological result and number of cores obtained in the first biopsy) and positivity in the second and third biopsies. Logistic regression analysis was performed to know which factors are predictors for positivity in 2nd and 3 th biopsies. According to the probabilities obtained, different risk groups were established. RESULTS 4.532 patients underwent prostate biopsy between 1999 and 2010. 663 patients were included for second biopsy and 191 for third biopsy. Detection rates for prostate cancer were 24,3% and 17.8% respectively. According to the multivariate analysis, the probability for positivity on second biopsy increases when first biopsy was sextant (p=0,049), patients were >65 years old (p=0,005) and PSA density was >0,15 (p=0,000). Four risk groups were established with a range of probability for prostate cancer between 7 and 37%. For third biopsy, predictive variables were: suspicious digital rectal examination (p=0,007), age >64 years (p=0,009), and PSA density >0,20 (p=0,001). Also risk groups were established with probabilities between 1,6 and 61%. CONCLUSIONS Detection rate for prostatic cancer in second and third biopsy is high. According to risk factors we can establish different risk groups.