Currently, no consensus exists on the best method for tumor quantification in prostate cancer (PCA), and its prognostic value remains controversial. We evaluated how a newly defined maximum tumor diameter (MTD) might contribute to the prediction of biochemical recurrence (BCR) in a consecutive series of PCA patients treated with radical prostatectomy (RP). Patients with PCA who underwent RP without neoadjuvant therapy at a single center were included for analysis. MTD was defined as the largest diameter of all identified tumors in all three dimensions (i.e., length, width, or depth) of the prostate ("Basel technique”). Cox regression models addressed the association of MTD with BCR in three risk groups (low risk—prostate-specific antigen (PSA) 20ng/ml or pT3 or GS ≥ 8) and whole cohort. Within a median follow-up of 44months (interquartile range (IQR) 23-66), 48 patients (9.4%) in the intermediate-risk and high-risk groups experienced BCR. In multivariate Cox regression analysis, PSA, pathological stage (pT stage), GS, positive surgical margins (PSMs), and MTD > 19.5mm were independent predictors for BCR (p 24.5mm) was the only independent predictor of BCR in the intermediate-risk group (hazard ratio (HR) 9.933, 95% confidence interval (CI) 2.070-47.665; p < 0.05). MTD is an independent risk factor of BCR in PC patients after RP. The combination of the MTD with other well-known prognostic factors after RP may improve decision-making concerning follow-up intensity or adjuvant treatment
