jueves, 14 de enero de 2010

Screening for Prostate and Breast Cancers - Have the benefits been overstated ?

Screening for prostate and breast cancers has been promoted heavily in the U.S., and annual screening costs are US$20 billion for just these two cancers. Lifetime diagnoses of prostate cancer were made in 1 of 11 white men in 1980; in 2009, the risk is 1 in 6. For breast cancer, risks were 1 in 12 in 1980 and 1 in 8 in 2009. Authors of a highly publicized review now challenge the value of such intensive screening.
If screening accurately identifies cancer at an early treatable stage, the incidence of localized cancer should increase after screening is implemented, and the incidence of metastatic cancer should decline. Because this pattern has occurred for neither breast nor prostate cancer, screening simply might identify low-risk non–life-threatening cancers that then are treated inappropriately with aggressive therapy.
By comparison, screening for colon and cervical cancers has led to significantly fewer cases of advanced disease. The observed decline in prostate cancer–related mortality in the last 20 years probably is not attributable to screening but, rather, to aggressive new adjuvant therapies. The costs associated with screening are substantial. For breast cancer, avoiding 1 cancer-related death requires annual screening of more than 800 women (age range, 50–70) for 6 years, which generates hundreds of biopsies and overly aggressive treatment for many patients with low-grade cancers.
The authors recommend greater focus on identifying new biomarkers that differentiate low- and high-risk cancers, minimalist approaches that are appropriate for treating patients with low-risk cancers, better tools to guide physicians and patients in informed decision making, and a greater focus on prevention and screening in high-risk patients rather than broad indiscriminate screening.
Original: Esserman L et al. Rethinking screening for breast cancer and prostate cancer. JAMA 2009 Oct 21; 302:1685

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