The influence of comorbidities on overall survival among older women diagnosed with breast cancer

Abstract

Background: Previous studies have shown that summary measures of comorbid conditions are associated with decreased overall survival in breast cancer patients. However, less is known about associations between specific comorbid conditions on the survival of breast cancer patients.

Methods: The Surveillance, Epidemiology, and End Results-Medicare database was used to identify primary breast cancers diagnosed from 1992 to 2000 among women aged 66 years or older. Inpatient, outpatient, and physician visits within the Medicare system were searched to determine the presence of 13 comorbid conditions present at the time of diagnosis. Overall survival was estimated using age-specific Kaplan-Meier curves, and mortality was estimated using Cox proportional hazards models adjusted for age, race and/or ethnicity, tumor stage, cancer prognostic markers, and treatment. All statistical tests were two-sided.

Results: The study population included 64,034 patients with breast cancer diagnosed at a median age of 75 years. None of the selected comorbid conditions were identified in 37,306 (58%) of the 64,034 patients in the study population. Each of the 13 comorbid conditions examined was associated with decreased overall survival and increased mortality (from prior myocardial infarction, adjusted hazard ratio [HR] of death = 1.11, 95% CI = 1.03 to 1.19, P = .006; to liver disease, adjusted HR of death = 2.32, 95% CI = 1.97 to 2.73, P < .001). When patients of age 66-74 years were stratified by stage and individual comorbidity status, patients with each comorbid condition and a stage I tumor had similar or poorer overall survival compared with patients who had no comorbid conditions and stage II tumors.

Conclusions: In a US population of older breast cancer patients, 13 individual comorbid conditions were associated with decreased overall survival and increased mortality.

Figures

Figure 1

Adjusted hazard ratios of comorbidities on all-cause mortality, stratified by age category, among breast cancer patients aged 66 years or older, Surveillance, Epidemiology, and End Results–Medicare 1992–2000. The hazard ratios were fully adjusted for race and/or ethnicity, stage category, grade category, estrogen receptor status, surgery, chemotherapy, radiation, and all other comorbid conditions. COPD = chronic obstructive pulmonary disease, PVD = peripheral vascular disease.

Figure 2

Kaplan–Meier survival curves by stage and each of 13 selected comorbid conditions (A–M) among women diagnosed with breast cancer at age 66–74 years, from the Surveillance, Epidemiology, and End Results–Medicare 1992–2000 database. CHF = congestive heart failure, COPD = chronic obstructive pulmonary disease, CRF = chronic renal failure, MI = myocardial infarction, PVD = peripheral vascular disease, RA = rheumatoid arthritis.

Figure 2

Kaplan–Meier survival curves by stage and each of 13 selected comorbid conditions (A–M) among women diagnosed with breast cancer at age 66–74 years, from the Surveillance, Epidemiology, and End Results–Medicare 1992–2000 database. CHF = congestive heart failure, COPD = chronic obstructive pulmonary disease, CRF = chronic renal failure, MI = myocardial infarction, PVD = peripheral vascular disease, RA = rheumatoid arthritis.