Stress and Breast Cancer
Douglas L. Delahanty
Kent State University
University of Pittsburgh Cancer Institute
A major theme in research on health and behavior has the impact of stress on the pathophysiology of disease and development of systemic dysfunction. Stress appears to be a major factor in the etiology of cardiovascular disease, AIDS, and several other chronic and/or life threatening illnesses. For disease states produced by years of slowly developing pathogenie conditions, this means identifying stressors and processes experienced over very long periods of time. This daunting task has made conclusions about stress and disease in humans tentative, and this literature requires cautious reading and interpretation. Nevertheless, research has produced suggestive evidence of the role of stress in a wide array of disease processes, including cancer. A growing area of investigation concerns stress as an etiological factor in breast cancer.
Each year, more than 184,000 American women are diagnosed with breast cancer, and 45,000 die from the disease (Parker, Tong, Bolden, & Wingo, 1996). Breast cancer is the most common cancer among women and is second only to lung cancer in mortality rates (Henderson, 1995). As with many cancers, until recently, relatively little was known about its etiology and progression. Researchers now know that some breast cancer is attributable to heritable genetic polymorphisms, some appears to be associated with lifetime estrogen exposure, and some to other major known risk factors (e.g., weight, age). There is also considerable variability of disease course among patients (Henderson, 1995) and the reasons for this variability are not well understood. Researchers have increasingly turned to psychological or behavioral variables to explain cases in which response to treatment and/or treatment outcomes vary (Andersen, 1994; Fox, 1983; Jensen, 1991).
Studies of the effects of stress on the development and pro been some researchers noting an association between stress and cancer outcomes (C. L. Cooper, R. Cooper, & Faragher, 1989; Funch & Marshall, 1983; Ramirez et al., 1989). Other investigations have not found associations between stress and disease outcomes (Cassileth, Lusk, D. S. Miller, Brown, & C. Miller, 1985; Greer & Morris, 1975; T. J. Priestman, S. G. Priestman, & Bradshaw, 1985). This chapter reviews the findings and limitations of studies examining the link between stress and breast cancer, concentrating on the extent to which stress and psychological factors contribute to the etiology and progression of breast cancer in women. Mechanisms through which stress may influence breast cancer are also discussed. This discussion does not review the larger literatures on stress and coping; these issues have been discussed elsewhere in this volume (see chap. 17).
The term cancer refers to a heterogeneous group of more than 100 specific types of cancer that are characterized by dysregulated and rapid cell growth and the potential for invasive or metastatic growth. Types of cancer vary considerably with regard to risk factors, etiology, disease course, and treatment. Depending on the site of the original tumor, its size, or whether it has metastasized, different cancers follow different courses and some appear to be related to stress. Some cancers are extremely aggressive, follow a very predictable disease