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).

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 course, and appear to progress inexorably as a function of biological factors (Levy & Wise, 1987). Others, including breast cancer, follow more variable disease courses, appear to be less exclusively affected by tumor biology, and appear to be affected by other factors. Investigators and clinicians have argued that the unexplained variance in the course of breast cancer may be due to psychosocial factors, and the impact of factors like stress on disease course has been examined at virtually every stage of breast cancer. The popular press has focused primarily on studies finding positive relations between psychosocial variables and breast cancer, and many popular books and magazine articles have instructed cancer patients that they can overcome cancer with their thoughts or by reducing distress (LeShan, 1977; Siegel, 1986). Methodological limitations alone suggest caution in interpreting such bold claims, and consequences of such lessons are also evident. If cancer patients believe they caused their cancer themselves or that they can prevent it from progressing, they may blame themselves, becoming depressed and less responsive to treatment and exacerbating their disease (Sapolsky, 1994). Scientific evidence of a direct link between psychological factors and cancer onset and progression lags far behind these popular assertions (Fox, 1983; Levenson & Bemis, 1991). . .