The effect of prostate volume on the yield of needle biopsy

Early diagnosis of prostate carcinoma has undergone significant evolution mainly due to the widespread use of serum prostate specific antigen, transrectal ultrasonography and spring loaded biopsy devices. A common dilemma faced by clinicians arises when a negative biopsy is obtained in a patient and there is a high suspicion for prostate carcinoma. The literature reveals a 20 to 40% positive repeat biopsy rate in men with elevated prostate specific antigen who had an initial negative biopsy. We determined the yield of 6 systematic sector biopsies as a function of total gland and peripheral zone volumes.

The database of transrectal ultrasound guided prostate needle biopsies performed at the Department of Urology, University of Washington Medical Center and Veterans Affairs Puget Sound Health Care System was reviewed. The yield of the 6 biopsies was determined as a function of the total gland and peripheral zone volumes.

A total of 1,057 men who underwent transrectal ultrasound guided prostate needle biopsies were investigated in our study. Of the men 326 were diagnosed with prostate cancer for a positive biopsy rate of 30.8%. No relationship between gland size and cancer yield was seen using total gland volume compared to the first quartile until the largest quartile when a significantly lower cancer detection rate was noted (odds ratio 1.5).

The positive yield of the systematic 6-sector biopsy decreases significantly when the total gland volume is greater than 55.6 cc or peripheral zone volume is greater than 33.61 cc. In men with smaller prostates 6 systematic sector biopsies should be adequate.