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Asian Journal of Andrology (2012) 14, 703–707; doi:10.1038/aja.2012.31; published online 9 July 2012
A novel equation and nomogram including body weight for estimating prostate volumes in men with biopsy-proven benign prostatic hyperplasia
Yasukazu Nakanishi1, Hitoshi Masuda1, Satoru Kawakami1, Mizuaki Sakura1, Yasuhisa Fujii2, Kazutaka Saito1, Fumitaka Koga1, Masaya Ito2, Junji Yonese2, Iwao Fukui2 and Kazunori Kihara1
1 Department of Urology, Tokyo Medical and Dental University, Tokyo 113-8519, Japan
2 Department of Urology, Cancer Institute Hospital, Tokyo 135-8550, Japan
Correspondence: Dr Y Nakanishi, (yasnak.uro@tmd.ac.jp)
Received 5 December 2011; Revised 24 February 2012; Accepted 1 March 2012
Advance online publication 9 July 2012.
| Abstract |
Anthropometric measurements, e.g., body weight (BW), body mass index (BMI), as well as serum prostate-specific antigen (PSA) and percent-free PSA (%fPSA) have been shown to have positive correlations with total prostate volume (TPV). We developed an equation and nomogram for estimating TPV, incorporating these predictors in men with benign prostatic hyperplasia (BPH). A total of 1852 men, including 1113 at Tokyo Medical and Dental University (TMDU) Hospital as a training set and 739 at Cancer Institute Hospital (CIH) as a validation set, with PSA levels of up to 20 ng ml−1, who underwent extended prostate biopsy and were proved to have BPH, were enrolled in this study. We developed an equation for continuously coded TPV and a logistic regression-based nomogram for estimating a TPV greater than 40 ml. Predictive accuracy and performance characteristics were assessed using an area under the receiver operating characteristics curve (AUC) and calibration plots. The final linear regression model indicated age, PSA, %fPSA and BW as independent predictors of continuously coded TPV. For predictions in the training set, the multiple correlation coefficient was increased from 0.38 for PSA alone to 0.60 in the final model. We developed a novel nomogram incorporating age, PSA, %fPSA and BW for estimating TPV greater than 40 ml. External validation confirmed its predictive accuracy, with AUC value of 0.764. Calibration plots showed good agreement between predicted probability and observed proportion. In conclusion, TPV can be easily estimated using these four independent predictors.
Keywords: body weight; equation; nomogram; prediction; prostate-specific antigen; prostate volume |
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