Prediction of the volume of large prostate cancers by multiple core biopsies

Objective. To evaluate whether large-volume prostate cancers can be predicted by means of multiple needle biopsies. Material and methods. In 115 men, 8-14 (mean 10) biopsies were taken, including eight from standardized positions (apex, mid-medial, mid-lateral and base). Biopsies were reviewed, the length of the cancer measured and the percentage cancer length calculated. All men underwent radical prostatectomy. The prostatectomy specimens were totally embedded and the tumor volume was measured planimetrically. The predictive values of the number and percentage of cores positive for cancer, cancer length and percentage cancer length were calculated for tumor volumes of >4, >6 and >8 ml. Results. Using univariate logistic regression, cancer length and percentage cancer length predicted tumor volumes of >4 (p < 0.001), >6 (p < 0.001) and >8 ml (p < 0.05). These measures were better predictors of tumor volume than the number and percentage of cores positive for cancer. A biopsy cancer length of >= 30 mm and a percentage cancer length of >= 25% predicted a tumor volume of >4 ml in 95% and 93% of cases, respectively. For tumor volumes of >6 or >8 ml, predictive values were lower. Tumor volumes of <2 and <4 ml were found in 13% and 35%, respectively of men with as many as six positive cores, indicating that the number of positive cores was less useful as a predictor of tumor volume than the cancer length. Conclusions. Cancer length and percentage cancer length are significant predictors of large tumor volumes. It is recommended that the linear extent of cancer in prostate biopsies should be reported by the pathologist.