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Example Data Analysis Exam Question
The Breast Cancer Surveillance Consortium (BCSC) collects longitudinal data on mammography examinations and breast cancer outcomes. The BCSC receives data from community mammography facilities. Data from mammography facilities consist of patient characteristics including age, family history of breast cancer, use of hormone therapy, and mammography characteristics such as the woman's breast density and the radiologist's assessments and recommendations. Data from mammography facilities are linked to cancer registries that collect data on all cancer cases occurring in the region. Thus if a woman is diagnosed with breast cancer following her mammogram, this information is available to the BCSC.
One of the objectives of the BCSC is to evaluate screening mammography accuracy. Screening mammography accuracy is assessed using the following measures: the proportion of women with cancers that are successfully detected by mammography (sensitivity); the proportion of women without cancer who are correctly identified as cancer-free by mammography (specificity); and the proportion of women who are recalled for additional evaluation who actually have cancer (positive predictive value). In studies of mammography, typically any cancer diagnosed within one year after a screening mammogram is considered to have been detectable at the time of the screening examination. Thus all cancers diagnosed within a year of the screening mammogram are used in assessing mammography accuracy. Previous studies have shown that accuracy varies depending on patient characteristics including, age, breast density, menopausal status, and availability of prior mammograms for comparison.
Radiologists' assessments of a mammogram are coded using the Breast Imaging Reporting and Data Systems (BI-RADS) scale. The assessment scores a radiologist can give a mammogram are:
The companies that manufacture mammography machines have been working to develop new technologies that will improve mammography accuracy. Over the past several years, they have introduced digital mammography machines, which have been replacing the traditional film mammography machines. Digital mammography has been shown to have superior accuracy to film-screen mammography for younger women and those with dense breasts. However, there is some evidence that digital mammography may not perform as well as film in older women. Questions remain as to how this new technology performs in women over 60 years of age.
Breast tissue is composed of fat and fibroglandular tissue. Fat is largely transparent to x-rays so tumors occurring in fatty tissue are easily visualized with mammography. Fibroglandular tissue is opaque to x-rays, making it more difficult to determine if a tumor is present in a breast with a higher proportion of fibroglandular tissue. Breasts with a higher proportion of fibroglandular tissue are termed "dense" breasts. Women with dense breasts are also more likely to have breast cancer. Because digital mammography is believed to perform better than film for women with dense breasts, these women may have been selectively seeking out digital mammography or may have been triaged to receive digital mammography by radiology facilities with both types of machines. As a result, breast density is associated with receipt of digital mammography as well as cancer risk and positive mammography results.
Using data from the BCSC on screening mammograms and subsequent cancer diagnoses from 2005-2008 for women age 60-89 years you will assess the accuracy of screening mammography and patient, mammography, and cancer characteristics that may be associated with accuracy. The following variables were measured at each mammogram visit (with some missing data). Missing values are due either to a woman failing to answer a question or the mammography facility failing to report this data to the BCSC. Women are recommended to undergo mammography screening annually or biennially, so some women have multiple mammograms included in the data set.
Specific questions to answer:
Carolina Mammography Registry | Metro Chicago Breast Cancer Registry | Kaiser Permanente Washington Registry | New Hampshire Mammography Network | Vermont Breast Cancer Surveillance System |
San Francisco Mammography Registry
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Last modified: June 2016
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