The percentage of core involved by cancer is the best predictor of insignificant prostate cancer, according to an updated definition (tumor volume up to 2.5 cm3): analysis of a cohort of 210 consecutive patients with low-risk disease.

To find out which factors could predict the diagnosis of insignificant prostate cancer (ins-PCa) according to a recently updated definition (overall tumor volume up to 2.5 cm(3); final Gleason score ≤6; organ-confined disease) on a prostatic biopsy specimen.This was a retrospective analysis of 210 patients undergoing radical prostatectomy for a cT1c prostate neoplasm with a biopsy specimen Gleason score of ≤6. A logistic regression model was used to assess the differences in the distribution of some possibly predictive factors between the ins-PCa patients, according to the updated definition, and the remaining patients.By applying an updated definition of ins-PCa, the prevalence of this condition increased from 13.3\% to 49.5\% (104 of 210 patients). The univariate analysis showed a statistically different distribution of the following factors: prostate-specific antigen density, prostate volume, number of cancer-involved cores, and maximum percentage of core involvement by cancer. At the multivariable analysis, the maximum percentage of involvement of the core retained its relevance (27.0\% in ins-PCa patients and 43.8\% in the remaining patients; hazard ratio, 0.972; P = .046), and a 20\% cutoff was detected.In a cohort of patients with PCa cT1c and a biopsy specimen Gleason score of ≤6, the ins-PCa rate, according to the updated definition, is close to 50\%, and the percentage of cancer involvement of the core is the single factor that best predicts this diagnosis.