Introduction 1 2 3 4 5 6 7 9 10 11 12 Therefore, in this present study, with a large cohort of 542 RP specimens, and a median follow-up of 39.5 months, we studied the prognostic value of MTD, as a surrogate for tumor volume, for BCR in patients with PC, with special attention to the high-risk group. Materials and methods 2 13 14 PSA values were obtained before surgery and at every follow-up point. BCR after RP was defined as two subsequent PSA levels above 0.10 ng/ml among patients who reached non-measurable levels after RP. Statistical analysis Baseline characteristics are summarized with median and interquartile ranges (IQR). Associations between MTD and clinical or pathological characteristics were examined by univariate regression models. Kaplan–Meier curves were used to assess the risk of BCR. Proportional hazards multivariable regression models were composed to determine prognostic factors for BCR. SPSS version 12.0.1 for Windows was used for all statistical analysis. Results 1 Table 1 n  Median IQR Age (years) 62.7 58.4–66.5 Follow-up period (months) 39.5 17.1–67.3 Pre-operative PSA (ng/ml) 8.0 5.5–13.0 Gleason score 6 5–7 n 2 1–3 3 1.6 0.6–3.4 3 2.0 0.8–3.9 Maximal tumor diameter (mm) 24.0 16.0–32.0 Data are presented as median and interquartile ranges (IQR) 2 n U P P P P P P r P r P r P r P r P Table 2 Associations between MTD and pathological characteristics  No. of patients Maximum tumor diameter Mean Median Range P a  T2 359 21.0 20.0 1–60 <0.001  T3a 116 30.8 28.0 12–60  T3b 52 31.1 31.0 3–55 a  ≤6 301 22.5 21.0 1–65 <0.001  3 + 4 136 26.2 25.0 8–60  4 + 3 22 25.0 24.0 3–49  ≥8 80 28.8 28.0 4–60 b  Negative 270 20.5 20.0 1–52 <0.001  Positive 271 28.5 28.0 3–65 b  1 241 27.3 26.0 1–65 <0.001  ≥1 301 22.3 22.0 1–50 a  <4 56 17.4 15.0 3–46 <0.001  4–10 289 23.6 24.0 1–55  10–20 123 24.5 24.0 2–55  >20 70 34.4 35.5 10–65 b  High  432 25.8 24.5 1–65 <0.001  Low/intermediate 72 14.3 14.0 1–36 P a b U P P 3 3 Table 3 Univariable and multivariable analysis of clinical and pathological characteristics associated with time to BCR Covariates Univariable Multivariable HR 95% CI AHR 95% CI Pre-operative PSA 1.02 1.01–1.04*   Pathological stage  pT2 1.0  1.0   pT3a 2.12 1.39–3.23* 1.26 0.81–1.97#  pT3b 3.90 2.33–6.53* 1.79 1.02–3.13* Gleason score  ≤6 1.0  1.0   3 + 4 2.64 1.64–4.25* 1.97 1.20–3.23*  4 + 3 7.27 3.18–16.63* 5.71 2.47–13.20*  ≥8 5.68 3.60–8.97* 3.57 2.17–5.89* Extracapsular extension 2.71 1.87–3.94*   Invasion seminal vesicle 3.07 1.94–4.87*   Margin status 4.64 3.02–7.12* 3.75 2.36–5.96* Number of tumors 1.02 0.88–1.17# 1.18 1.02–1.36* Maximal tumor diameter 1.02 0.99–1.04#   Index tumor volume 1.04 1.02–1.07*   Total tumor volume 1.04 1.02–1.07*   HR CI AHR P P Discussion 2 12 3 11 15 P P 16 P Another striking difference is the percentage of positive surgical margins. In our study this is relatively high (50%) compared to other studies (Renshaw et al. 31 and 26%, Eichelberger et al. 23%, Dvorak et al. 27%). Our median BCR rate (21% after 39.5 months), however, was comparable to the median of these studies [Renshaw 27% (22.5 months), Eichelberger 12% (12 months), Dvorak 31% (64.8 months)]. An explanation for the high number of positive surgical margins, next to surgical techniques, is that by evaluating only partially included prostates you miss positive surgical margins. 17 Finally, none of the mentioned studies separately looked at the group where prediction might be of most importance, the high-risk group. As clearly indicated, in this group, neither MTD nor TV is of any significant value. In all, we do not advice to use MTD as a prognostic factor for BCR, since after proper follow-up and with adequate pathological techniques it does not add anything to other readily available prognostic factors. Moreover, in the high-risk group, TV is not an independent prognostic factor at all. Conclusions The results of our study suggest that MTD is positively correlated to total TV, as can be expected. MTD was weakly associated with risk of BCR and this association was lost in the high-risk group. If adjusted for positive surgical margins, higher Gleason score, advanced pathological stage, and multiple tumors, MTD did not provide additional information.