Finasteride may not be related to high-grade tumors

August 15, 2005

San Antonio--A study relating prostate size to tumor grade presented here at the AUA annual meeting appears to dispel the concern that finasteride (Proscar) as a prophylaxis for prostate cancer might increase the incidence of higher-grade tumors.

"Finasteride may in fact be a chemopreventive agent that is safe and effective at preventing prostate cancer. The increase in higher-grade tumors in men with smaller prostates seen in the Prostate Cancer Prevention Trial is more than likely a sampling artifact. The increase seen in the [finasteride arm] of the trial may result from prostate volume reduction," Girish Kulkarni, MD, a urology resident at the University of Toronto, told Urology Times.

To arrive at these conclusions, Dr. Kulkarni, Neil Fleshner, MD, and colleagues looked at 369 transrectal ultrasound-guided sextant biopsies conducted at the hospital during the past 3 years. Study criteria required that the patients' PSA levels be ≤10.0 ng/mL, the TRUS biopsy be taken at the Toronto institution, and that subsequent radical prostatectomy also be conducted at the same institution.

"Patients with small glands and high-grade tumors on biopsy also tended to have high-grade tumors on analysis following prostatectomy," Dr. Kulkarni said. "In other words, there tended to be very little upgrading in patients with small prostates, meaning that the sextant biopsies were obtaining adequate samples. In patients with larger glands, however, there was significant upgrading [at prostatectomy], which indicates a poorer sampling of the gland."

"These results mirror those seen in the PCPT, with a higher proportion of high-grade tumors being diagnosed in smaller glands at biopsy. However, if we examine the histological 'truth' at radical prostatectomy, the proportion of high-grade tumors is the same across all volume categories. It is clear that the sextant biopsy technique leads to a grade-artifact amongst larger prostate glands," said Dr. Kulkarni.

Several other findings jumped from the data in the study.

"We had a high rate of Gleason 7 tumors at biopsy and at radical prostatectomy. At biopsy, it was around 52%, which is higher than is seen in the literature. In the Prostate Cancer Prevention Trial, it was around 30%. We are not really sure of why this is. It may be related to a referral bias," Dr. Kulkarni explained.

"Another surprising finding was that 65% of our patients had hypoechoic lesions and that these lesions were predictors of high-grade disease," he added. "Historically, a hypo-echoic lesion has had a 50/50 chance of being a tumor, but we are beginning to question this dictum. Our radiologist is conducting a study of whether hypoechoic lesions are predictors of prostate cancer, particularly of high-grade cancer."