The Relationship of Prostate Gland Volume to Extended Needle Biopsy on Prostate Cancer Detection

Abstract

We investigated the relationship between prostate volume and cancer detection by needle biopsy, and determined the effect of an increased number of cores on the sampling error of needle biopsy on large prostate glands. The study cohort included 750 consecutive patients who underwent first time transrectal ultrasound guided prostate needle biopsy from January 1995 to August 2001. Prostate volumes were divided into quartiles (13 to 34, 34.1 to 45, 45.1 to 64 and 64.1 to 244 cc). Multivariate analysis controlling for age, prostate specific antigen (PSA) and biopsy indication was performed to determine the effect of the number of cores and prostate volume on prostate cancer detection. Patients diagnosed with prostate cancer were older (p = 0.0035) and had higher PSA levels (p = 0.0002) than those with no cancer on biopsy. Decreasing cancer detection rates were seen with increasing prostate volume (p = 0.0074). The OR of detection for each additional core was 0.99 (95% CI 0.93, 1.06), suggesting that increasing the number of biopsy cores did not increase the rate of prostate cancer detection. Multivariate analysis revealed that patients with larger prostates had the same, or possibly lower, cancer detection rate as the number of biopsy cores was increased. Patients with larger prostates were older (p <0.0001), had higher PSA levels (p <0.0001) and were even more likely to have undergone biopsy for increased PSA rather than abnormal digital rectal examination alone (p <0.0001). Our study suggests that the lower cancer detection rate for men with large prostates may be due to a decrease in the use of increased serum PSA for prostate cancer detection in larger prostates in addition to other factors such as sampling error. Increased serum PSA levels in cases of larger prostates, although a risk factor for prostate cancer warranting biopsy, may also be due to nonmalignant sources such as benign prostatic hyperplasia.