Putting it all together: How do primary care physicians interpret and use the results of prevention trials?

CS16-03

Aspirin chemoprevention for cardiovascular disease has been used widely since trials demonstrated its effectiveness were published. Cancer chemoprevention, however, has been used much less widely, despite publication of well-done randomized controlled trials. In 1998, tamoxifen was shown to reduce breast cancer incidence by about 50% compared with placebo in the NSABP's Breast Cancer Prevention Trial. In 2003, results from the Prostate Cancer Prevention Trial showed that finasteride reduced biopsy-detected prostate cancer incidence by about 25% compared with placebo. Despite the significant incidence and death rate of breast and prostate cancer and a high level of public concern about these diseases, a non-systematic review of the literature suggests that update of drugs for breast and prostate cancer chemoprevention has been low. Only a few studies have investigated the use of tamoxifen for breast cancer chemoprevention by primary care physicians and no studies about the use of finasteride for prostate cancer chemoprevention in primary care practice were identified. Even among women at increased risk for breast cancer based on Gail model risk factors, interest in and use of tamoxifen is low. The US Preventive Services Task Force has issued a recommendation on breast cancer chemoprevention but has not included prostate cancer chemoprevention on a list of new topics under review. Low use of cancer chemoprevention drugs by primary care physicians may be due to a number of reasons, including: 1) concern by both physicians and patients about side effects/harms of drugs taken by healthy people; 2) uncertainty about length of time needed for benefit; 3) discomfort using a drug (tamoxifen) for chemoprevention that is also used for cancer treatment; 4) lack of patient demand for cancer chemoprevention; 5) high cost of chemopreventive agents; 6) time and effort needed to assess risk and engage in shared decision-making for chemoprevention; 7) lack of familiarity with results of chemoprevention studies; and 8) low confidence in effectiveness of chemoprevention (compared with treatment). More research is needed to understand the importance and prevalence of these possible barriers among primary care physicians. The authors are conducting a study of prostate cancer chemoprevention by primary care physicians and urologists in the Veterans Healthcare Administration. Ultimately, the increased use of cancer chemopreventive agents will require the development of less expensive and safer choices. These drugs will need to be promoted effectively to both physicians and people at increased risk for cancer.