The effect of comorbidity on 3-year survival of women with primary breast cancer.

To determine the effect of comorbidity and stage of disease on 3-year survival in women with primary breast cancer. Longitudinal, observational study. Metropolitan Detroit. 936 women ages 40 to 84 years. Data on stage of breast cancer, treatment type, and comorbidity were obtained from Metropolitan Detroit Cancer Surveillance System (MDCSS) files and medical records. Personal interviews were the source of information on social and behavioral factors. Vital status and cause of death were obtained from MDCSS files. Patients who had 3 or more of 7 selected comorbid conditions had a 20-fold higher rate of mortality from causes other than breast cancer and a 4-fold higher rate of all-cause mortality when compared with patients who had no comorbid conditions. The effects of comorbidity were independent of age, disease stage, tumor size, histologic type, type of treatment, race, and social and behavioral factors. Moreover, women with severe comorbid conditions had uniformly higher mortality rates, and early diagnosis in these women conferred no survival advantage. Comorbidity in patients with breast cancer appears to be a strong predictor of 3-year survival, independent of the effects of breast cancer stage. This finding suggest that trials assessing the efficacy of screening should routinely include measures of comorbidity.