The person-years saved model and other methodologies for assessing the population impact of cancer-prevention strategies.
The results of the Prostate Cancer Prevention Trial spurred debate because finasteride was found to reduce the period prevalence of prostate cancer by about 25% while also increasing the rate of high-grade prostate cancers. Assessing how finasteride would impact mortality at the population level is key to evaluating the public health implications of these results. Any model for evaluating the impact of chemoprevention at the population level will involve methods for assigning weights to competing outcomes of the chemoprevention. The person-years saved model, which uses survival to weigh outcomes, assesses the impact on population mortality and has particular strengths. The person-years saved model shows that more than 300,000 person-years would be saved during a period of 10 years with the widespread use of finasteride, assuming no change in the rate of high-grade prostate cancers. The rate of high-grade prostate cancers in the population, about 20% in any given year, would have to nearly triple to 60% for the net positive impact of finasteride to be zero. The person-years saved model shows that the administration of finasteride is likely to result in a net positive impact of finasteride on population mortality, even with an increase in the rate of high-grade prostate cancers. Future models may use other outcomes to assess population impact, including economic, quality-of-life, or various combinations of outcomes.