Comparison of prostate cancer tumor volume and percent cancer in prediction of biochemical recurrence and cancer specific survival

Abstract

Objectives Tumor volume and percent cancer (ratio of tumor volume/prostate volume) have been proposed as predictors of biochemical recurrence and cancer specific survival after radical prostatectomy. However, their relative merits as prognosticators have not been tested. We therefore evaluated and compared tumor volume and percent cancer as independent predictors of biochemical recurrence and prostate cancer specific death after radical prostatectomy. Methods and Materials A retrospective review of 739 patients who underwent radical prostatectomy for prostate cancer between 1984 and 2004 was conducted. Median follow-up was 91.7 months, and 22 patients died of prostate cancer. Univariate and multivariate analysis evaluated the following factors in predicting biochemical recurrence and prostate cancer specific death: tumor volume, prostate volume, percent cancer, Gleason score, percentage of Gleason grade 4/5, margin status, capsular invasion status, seminal vesicle invasion status, preoperative PSA, and lymph node status. Results In univariate analysis, both tumor volume ( P < 0.001) and percent cancer ( P < 0.001) significantly correlated with biochemical recurrence. Since they are highly correlated, they did not predict outcome independently when included in the same model; however, both were highly predictive for biochemical recurrence in separate multivariate models ( P = 0.01 for both). Both also correlated with cancer specific survival as single variables; however, in separate multivariate models, only tumor volume ( P = 0.03) predicted death, while percent cancer did not ( P = 0.09). Conclusions Tumor volume and percent cancer are independent predictors of recurrence after radical prostatectomy. However, in our series, tumor volume predicted cancer specific death better than percent cancer. Therefore, accurate determination of tumor volume, along with other accepted pathologic indices, is sufficient and preferred over percent cancer for prognostication after radical prostatectomy.