Assessing benefit and risk in the prevention of prostate cancer: the prostate cancer prevention trial revisited.
OBJECTIVE
The Prostate Cancer Prevention Trial demonstrated a 25% reduction in period prevalence of prostate cancer in men randomly assigned to 5 mg/d of finasteride. However, widespread use of finasteride for prevention is inhibited by the observed increased risk of high-grade disease. We present a model of risk and benefit that estimates the potential effects of histologic artifact in the assignment of excess risk for high-grade disease and the possible effect of overdetection bias introduced by finasteride-induced volume reduction.


METHODS
The absolute benefit/absolute risk ratio of finasteride use was estimated by calculating the ratio of absolute risk reduction in the finasteride arm to the absolute risk of excess high-grade cancers. This ratio was recalculated for assumptions that 10%, 25%, or 50% of the excess high-grade cancers were due to histologic artifact, and that there was a 25% overdetection bias in the finasteride arm.


RESULTS
For all cancers the absolute benefit/absolute risk ratio increased from 4.6:1 to 5.1:1, 6.2:1, and 9.2:1 for assumptions of 10%, 25%, or 50% histologic artifact, respectively. The ratio increased from 4.6:1 to 8.2:1 for the assumption of 25% overdetection bias, and to 9.1:1, 10.9:1, and 16.3:1 for combined assumptions of 25% overdetection bias and 10%, 25%, or 50% histologic artifact, respectively.


CONCLUSIONS
The adoption of a prevention strategy hinges on potential benefits weighed against potential risks. This model demonstrates the magnitude of effect for a hypothesized range of histologic artifact and overdetection bias on the assessment of risk versus benefit for finasteride.
Klein
Eric A
EA
Section of Urologic Oncology, Glickman Urological Institute, Cleveland, OH 44195, USA. kleine@ccf.org
Tangen
Catherine M
CM
Goodman
Phyllis J
PJ
Lippman
Scott M
SM
Thompson
Ian M
IM
D000230:Adenocarcinoma / Q000517:prevention & control*; D001707:Biopsy, Needle; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D018120:Finasteride / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D009367:Neoplasm Staging; D016017:Odds Ratio; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000517:prevention & control*; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D016896:Treatment Outcome
D004791:Enzyme Inhibitors; D018120:Finasteride