['We evaluated tumor size, measured as the percent of the prostate involved by cancer, as a predictor of tumor recurrence after radical prostatectomy in patients with pathologically organ confined prostate cancer.', 'One of us (WJC) performed radical retropubic prostatectomy in 1,850 men who had pathologically organ confined prostate cancer with tumor size recorded between January 1988 and February 2003. The percent of prostate tissue involved by carcinoma in the radical prostatectomy specimen was estimated by visual inspection. We compared clinicopathological characteristics in patients who did and did not have tumor recurrence and stratified them by percent of tumor in the prostatectomy specimen. We also evaluated the relationship between percent of cancer and biochemical evidence of cancer recurrence.', 'Patients who had recurrence were slightly older (mean age 62 vs 60 years, p = 0.004), and had higher mean preoperative prostate specific antigen (8.6 vs 6.3 ng/ml, p <0.0001) and a higher proportion of poorly differentiated tumors (Gleason grades 8 to 10) (7% vs 1%, p = 0.001). The mean percent of cancer was higher in men with recurrence (11% vs 7%, p <0.0001). Men with 10% or greater of the gland involved by cancer had a 10% recurrence rate compared with a 5% rate in men in whom cancer involved less than 10% of the gland (p = 0.001). The 5-year recurrence-free survival rate was 94%, 91% and 82% in patients with less than 10%, 10% to 20% and greater than 20% of the gland involved. The multivariate Cox model indicated that the percent of cancer involvement of the prostate provides unique predictive information about the risk of cancer recurrence (p = 0.0001). The estimated 5-year recurrence-free survival rate based on the Cox model indicated that patients with greater than 20% of the gland involved by tumor, clinical stage T2/T3 and Gleason sum >/=7 were at substantial risk of cancer recurrence.'] Is percent carcinoma in prostatectomy specimen associated with risk of recurrence after radical prostatectomy in patients with pathologically organ confined prostate cancer?