screening, although they are now moving more toward assessing the quality of diagnosis and management. Research studies on quality of cancer care have been limited, with most research concentrating on cancers with comparatively higher prevalence and more evidence supporting clinical practice. In this section, the evidence of cancer care quality problems is assessed for breast and prostate cancer.
Breast cancer is the most commonly diagnosed non-skin cancer among American women, and it is estimated that one in eight women will develop breast cancer in her lifetime (Ries et al., 1998). In 1999, 176,300 new breast cancer diagnoses are expected (ACS, 1999). Although lung cancer has surpassed breast cancer as the leading cause of cancer deaths in women, breast cancer still accounts for 43,300 deaths annually (ACS, 1999). Breast cancer remains a common illness with significant morbidity and mortality.
Among oncologic conditions, breast cancer has one of the most extensive scientific literatures to support a strong association between processes of care and outcomes. Unlike many malignancies, effective interventions exist for breast cancer that decrease mortality and improve quality of life. In addition, evidence from the literature suggests that all phases of the continuum of care have an important effect on breast cancer outcomes, including early detection, diagnostic evaluation, and treatment. This extensive clinical literature, with many well-designed randomized controlled trials, provides a firm grounding for the development of process measures in breast cancer. However, even in breast cancer, not every aspect of the continuum of care has been studied to determine its effect on outcomes. Thus, even for this heavily studied disease, some of the presumed associations between process and outcomes reflect consensus within the medical community and expert opinion and are not based upon reliable evidence.
Although there has been controversy over the age at which one should begin screening for breast cancer, data from multiple randomized trials and several meta-analyses provide evidence that screening with mammography results in diagnosis at an earlier stage and in better outcomes. Early detection of breast cancer through screening mammography has been shown to reduce mortality by 20 to 39 percent for women ages 50 years and older (Nyström et al., 1993; Roberts et al., 1990; Shapiro et al., 1988). Also, results for women age 40 to 50 have shown a trend toward reduced mortality ranging from 13 to 23 percent (Kerlikowske et al., 1995; Tabar et al., 1995). Although the associated benefits and risks are controversial, many professional and public health organizations, including both the American Cancer Society and the National Cancer Institute, currently recommend screening mammography beginning at age 40 (Eastman, 1997; Mettlin and Smart, 1994).
For screening mammography to be effective, abnormalities identified at screening must be evaluated appropriately. Mammography is one of the most technically challenging radiological procedures, and ensuring the quality of the image is difficult. Furthermore, according to radiological experts, mammograms are the most difficult radiographic images to read (USGAO,