The NCI – funded PLCO trial is a 16-year randomized control study that began in 1993. It is accruing 74,000 men aged 60 to 74 years and has a design power of 90% to determine 20% reduction of prostate cancer mortality. PLCO will provide important information about the efficacy of screening. A second large randomized trial, the European Randomized Study of Screening for Prostate Cancer and PLCO trials are collaborating to share data to increase statistical power. Results from these trials are expected in 2005 to 2008. Finally, based on a randomized study in Sweden of 9972 men aged 50 to 65 years, it was concluded that it is safe to screen biennially in men with PSA of less than 2 ng/mL, with different screening intervals determined based on baseline PSA. Further confirmation of appropriate screening intervals for PSA screening is needed.
As is the case for other kinds of cancer screening, there is concern about over diagnosis for prostate cancer. In fact, it is an even greater potential problem for prostate than for some other kinds of cancer screening because of studies showing that many men die or prostate cancer without ever having known they had the disease. Draisma et al attempted to provide some insight into the potential over diagnosis problem using models to simulate lead time. They estimated that annual screening from age 55 to 67 years would result in an over detection rate of 50% and the lifetime prostate cancer risk was increased to 80%. People will argue whether the model is correct, and all models have imprecision. Nevertheless, this is further caution about the limitations of screening for prostate cancer, the need for better understanding of the biology of the disease, and the parallel need for better screening tests.
Trends and What They Mean
National data from 1990 to 1966 show that prostate cancer incidence peaked in 1992 at 190.8 per 10,,000 and declined at an average rate of 8.5% from 1992 to 1996. A series of related reports in the Journal of the National Cancer Institute, based on data from the Surveillance, Epidemiology, and End Results Cancer Registry program show a decline in incidence of regional stage disease, as well as a decline in incidence-based mortality trends for localized and distant stage disease. Statistical methods were applied to consider the effect of screening by limiting some analysis to the contribution from cases diagnosed since 1987, when widespread screening using the PSA test had occurred. In a review of published data from five prospective trials, treatment of localized disease was associated with a marked decrease in prostate cancer deaths. Thus some evidence shows improved prognosis for screen-detected cases. However, alternative interpretations, such as the possibility that cause-of-death mis-classification could explain these findings, cannot be ruled out.
As is the case for other kinds of cancer screening, there is concern about over diagnosis for prostate cancer. In fact, it is an even greater potential problem for prostate than for some other kinds of cancer screening because of studies showing that many men die or prostate cancer without ever having known they had the disease. Draisma et al attempted to provide some insight into the potential over diagnosis problem using models to simulate lead time. They estimated that annual screening from age 55 to 67 years would result in an over detection rate of 50% and the lifetime prostate cancer risk was increased to 80%. People will argue whether the model is correct, and all models have imprecision. Nevertheless, this is further caution about the limitations of screening for prostate cancer, the need for better understanding of the biology of the disease, and the parallel need for better screening tests.
Trends and What They Mean
National data from 1990 to 1966 show that prostate cancer incidence peaked in 1992 at 190.8 per 10,,000 and declined at an average rate of 8.5% from 1992 to 1996. A series of related reports in the Journal of the National Cancer Institute, based on data from the Surveillance, Epidemiology, and End Results Cancer Registry program show a decline in incidence of regional stage disease, as well as a decline in incidence-based mortality trends for localized and distant stage disease. Statistical methods were applied to consider the effect of screening by limiting some analysis to the contribution from cases diagnosed since 1987, when widespread screening using the PSA test had occurred. In a review of published data from five prospective trials, treatment of localized disease was associated with a marked decrease in prostate cancer deaths. Thus some evidence shows improved prognosis for screen-detected cases. However, alternative interpretations, such as the possibility that cause-of-death mis-classification could explain these findings, cannot be ruled out.
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