Korean J Urol.  2011 Jan;52(1):24-30.

Significance of Predicted Tumor Volume as a Predictor of Pathologic Stage in Patients Undergoing Radical Prostatectomy

• Ku JH
• Moon KC
• Kwak C
• Kim HH

Abstract

PURPOSE
The purpose of this study was to evaluate whether predicted tumor volume could predict pathologic stage in patients undergoing radical prostatectomy.
MATERIALS AND METHODS
The clinical and pathologic data of 236 patients who underwent a 12-core needle biopsy followed by radical prostatectomy were obtained from our database and reviewed retrospectively.
RESULTS
Observed tumor volume correlated best with serum prostate-specific antigen (PSA) level (r=0.677, p<0.001) and the number of positive biopsy cores (r=0.489, p<0.001). Stepwise multiple linear regression analysis was used to develop a model for predicting tumor volume before radical prostatectomy. All explanatory variables except PSA and the number of positive biopsy cores were eliminated, yielding the equation ([predicted tumor volume]=0.381x[PSA]+0.921x[No. of positive biopsy cores]-0.992). Tumor volume predicted by this equation correlated strongly with observed tumor volume (r=0.722, p<0.001). This was also true when a different cohort of 159 patients was analyzed (r=0.638, p<0.001). The areas under the receiver operating characteristic curves of predicted tumor volume were 68.5% for extracapsular extension, 75.7% for seminal vesicle invasion, and 70.4% for positive surgical margin. Kaplan-Meier curves revealed that predicted tumor volume correlated significantly with biochemical recurrence-free survival (p<0.001; log-rank test).
CONCLUSIONS
Our findings suggest that tumor volume predicted on the basis of PSA levels and number of positive biopsy cores may predict pathologic stage with reasonable accuracy.

Keyword

Prostatectomy; Prostatic neoplasms; Treatment outcome; Tumor burden

MeSH Terms

Biopsy
Biopsy, Needle
Cohort Studies
Humans
Linear Models
Prostate-Specific Antigen
Prostatectomy
Prostatic Neoplasms
ROC Curve
Seminal Vesicles
Treatment Outcome
Tumor Burden
Prostate-Specific Antigen

Figure

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  FIG. 1 (A) Regression analysis showing the correlation between observed tumor volume and predicted tumor volume (r=0.722, p<0.001), for which predicted tumor volume was calculated by using the following equation: [Predicted tumor volume]=0.381x[prostate-specific antigen]+0.921×[No. of positive biopsy cores]-0.992. (B) Bland-Altman analysis of the agreement between observed tumor volume and predicted tumor volume. The linear line indicates the mean difference. Dotted lines represent 95% confidence intervals from the mean of the two volumes.

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  FIG. 2 Ability of predicted tumor volume to predict pathologic outcomes. (A) Extracapsular extension. (B) Seminal vesicle invasion. (C) Positive surgical margin.

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  FIG. 3 Biochemical recurrence-free survivals of patients according to median predicted tumor volume (p<0.001; log-rank test).

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  FIG. 4 Observed and predicted tumor volumes of a second cohort of patients who underwent radical retropubic prostatectomy between 2005 and 2006. (A) Regression analysis of all 159 patients (r=0.638, p<0.001). (B) Bland-Altman analysis of all 159 patients. (C) Regression analysis of the 66 patients whose observed tumor volume was <3 ml (r=0.277, p=0.024). (D) Bland-Altman analysis of the 66 patients whose observed tumor volume was <3 ml.

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