Dr. Petitti/Research Design II
This was another good lecture by Dr. Petitti. She skillfully provides examples, when explaining research methods. Of particular note, was her discussion of the United States Preventitive Services Task Force and the new recommendations for breast cancer screening. Upon review, I wish we had been provided with even greater detail. It seems 2 studies were done, totalling 500,000 Chinese women. My question about the studies would be whether the study of a single population group would properly reflect and correlate with American women. Diets, in particular are not the same, and couldn't this skew the study.
FYI-
Summary of Recommendation
•The U.S. Preventive Services Task Force (USPSTF) recommends screening mammography, with or without clinical breast examination (CBE), every 1-2 years for women aged 40 and older.
Rating: B recommendation.
Rationale: The USPSTF found fair evidence that mammography screening every 12-33 months significantly reduces mortality from breast cancer. Evidence is strongest for women aged 50-69, the age group generally included in screening trials. For women aged 40-49, the evidence that screening mammography reduces mortality from breast cancer is weaker, and the absolute benefit of mammography is smaller, than it is for older women. Most, but not all, studies indicate a mortality benefit for women undergoing mammography at ages 40-49, but the delay in observed benefit in women younger than 50 makes it difficult to determine the incremental benefit of beginning screening at age 40 rather than at age 50.
The absolute benefit is smaller because the incidence of breast cancer is lower among women in their 40s than it is among older women. The USPSTF concluded that the evidence is also generalizable to women aged 70 and older (who face a higher absolute risk for breast cancer) if their life expectancy is not compromised by comorbid disease. The absolute probability of benefits of regular mammography increase along a continuum with age, whereas the likelihood of harms from screening (false-positive results and unnecessary anxiety, biopsies, and cost) diminish from ages 40-70. The balance of benefits and potential harms, therefore, grows more favorable as women age. The precise age at which the potential benefits of mammography justify the possible harms is a subjective choice. The USPSTF did not find sufficient evidence to specify the optimal screening interval for women aged 40-49 (go to Clinical Considerations).
•The USPSTF concludes that the evidence is insufficient to recommend for or against routine CBE alone to screen for breast cancer.
Rating: I recommendation.
Rationale: No screening trial has examined the benefits of CBE alone (without accompanying mammography) compared to no screening, and design characteristics limit the generalizability of studies that have examined CBE. The USPSTF could not determine the benefits of CBE alone or the incremental benefit of adding CBE to mammography. The USPSTF therefore could not determine whether potential benefits of routine CBE outweigh the potential harms.
•The USPSTF concludes that the evidence is insufficient to recommend for or against teaching or performing routine breast self-examination (BSE).
Rating: I recommendation.
Rationale: The USPSTF found poor evidence to determine whether BSE reduces breast cancer mortality. The USPSTF found fair evidence that BSE is associated with an increased risk for false-positive results and biopsies. Due to design limitations of published and ongoing studies of BSE, the USPSTF could not determine the balance of benefits and potential harms of BSE.
This information came directly from the following website, which provides much more detail, if you're interested.
http://www.ahrq.gov/clinic/3rduspstf/breastcancer/brcanrr.htm
Further, and on another note, she confirmed my suspicions that much medical research is done for the sake of research. For many years I have pondered the purpose of a study with 10-50 participants. Much medical literature is based on these small study sizes. However, now armed with Power Calculations to aid in our assessments of test validity, we can make informed decisions about existing studies, as well as plan for our own valid research.
Lee
