The effect of age and comorbidity in the treatment of elderly women with nonmetastatic breast cancer

Background: Increasing age has most often been associated with less aggressive approaches to treatment of nonmetastatic breast cancer in elderly women even after controlling for stage of disease at diagnosis. Objective: To examine the influence of patient age on the initial treatment for breast cancer received by elderly women while controlling for the effect of patient comorbidity. Methods: Cancer registry records for a cohort of 2252 women aged 66 years or older who were diagnosed as having nonmetastatic, invasive breast cancer between 1984 and 1989 and identified through the Virginia Cancer Registry were linked to-Medicare Provider and Reimbursement data files. Multivariate models were used to assess the effects of age and comorbidity (as measured by the International Classification of Diseases, Ninth Edition, codes recorded on Medicare claims) on initial treatment approach while adjusting for stage of disease, race, residential location, marital status, and year of diagnosis. Results: In baseline multivariable models, age was negatively associated with any surgical treatment, non-breast-conserving procedures, and radiotherapy following breast-conserving surgery. The odds of women aged 85 years and older receiving surgery were less than one third those of women aged 66 to 74 years (odds ratio, 0.31; 95% confidence interval, 0.16 to 0.60), while odds ratios across the same two age groups for nonbreast-conserving surgery and adjuvant radiotherapy were 0.55 (95% confidence interval, 33 to 92) and 0.03 (confidence interval, 0.01 to 0.13), respectively. With additional adjustment for aggregate comorbidity, odds ratio estimates in these same age-group comparisons were virtually unchanged at 0.31, 0.56, and 0.04. Conclusion: Aggregate comorbidity measured by inpatient International Classification of Diseases, Ninth. Edition, codes on Medicare inpatient hospital claims does not explain age-related patterns in the initial treatment of elderly patients with breast cancer.