Imaging-measured prostate volumes are different between patients with confined and extraprostatic prostate cancer. The purpose of this study was to determine whether the prostate volume measured by magnetic resonance imaging (MRI) or transrectal ultrasonography (TRUS) was of incremental predictive value for organ-confined prostate cancer after considering preoperative prostate-specific antigen level, biopsy Gleason score, and clinical stage.

We retrospectively reviewed 1071 and 1201 consecutive patients who had undergone MRI or TRUS prostate volume measurement from 1983 to 2003. We controlled for other factors such as biopsy-derived Gleason score, preoperative serum prostate-specific antigen level, and clinical stage. Two statistical models, one incorporating MRI data and one TRUS data, were developed to predict for organ-confined prostate cancer. The models were subjected to bootstrapping by resampling 200 times to reduce bias when estimating the areas under the receiver operating characteristic curve.

In both statistical models, preoperative prostate-specific antigen (P <0.001), biopsy Gleason score (P <0.001), and clinical stage (P <0.001) were significant predictors for organ-confined prostate cancer. The MRI volume (P <0.001) and TRUS volume (P <0.001) were incremental predictors in their respective models. However, the area under the receiver operating characteristic curve increase was 1% and 2% for TRUS and MRI, respectively.

The preoperative volume of the prostate measured by either MRI or TRUS can be used to predict for organ-confined prostate cancer. However, the value of adding the prostate volume as a variable on its own to the prediction model is limited.