Factors Associated With Surgical and Radiation Therapy for Early Stage Breast Cancer in Older Women

BACKGROUND: In addition to demographic and health care-related characteristics, the age and physiologic status of women at the time of breast cancer diagnosis have been reported to influence receipt of standard treatments. Previous studies of the influence of age and comorbidity have not examined whether other patient-, region-, or health care-related characteristics altered the association of age and comorbidity with type of treatment received. PURPOSE: This study examined factors associated with receipt of breast-conserving surgery and radiation therapy, both of which are recommended treatments for breast cancer, among a cohort of 18,704 women aged 65 years or more who had breast cancer diagnosed during the period from 1985 through 1989. METHODS: A data file linking Medicare claims records to data from the Surveillance, Epidemiology, and End Results (SEER) Program of the U.S. National Cancer Institute was utilized. Logistic regression analysis was used to examine associations between patient, region, and hospital characteristics and the receipt of specific treatments. The likelihood test was used to assess the significance of observed associations (expressed as odds ratios ORs). Because of multiple comparisons, only those ORs with two-sided P values <.01 were considered statistically significant. RESULTS: The frequency of breast-conserving surgery was highest (54%) among women aged 80 years or more, who had two or more comorbid conditions and stage I disease. However, in general, the receipt of radiation therapy among women undergoing breast-conserving surgery declined markedly with age, irrespective of comorbidity status and disease stage. Between the ages of 65-69 years and 80 years or older, radiation therapy declined from 77% to 24% among women with no comorbid conditions and from 50% to 12% among women with two or more comorbid conditions. In regression models that included hospital, region, and patient characteristics as variables, age and comorbidity remained independently associated with the receipt of radiation therapy (OR = 0.12 and 95% confidence interval CI = 0.10-0.14 for women aged 80 years or more compared with women 65-69 years of age and OR of 0.33 95% CI = 0.24-0.46 for women with two or more comorbid conditions versus no comorbid conditions). CONCLUSIONS: After adjustment for multiple clinical and nonclinical factors influencing treatment, chronologic age remains an important independent factor associated with the receipt of radiation therapy after breast-conserving surgery among women aged 65 years or more who were diagnosed with early stage breast cancer. IMPLICATIONS: Future studies should determine whether these differences in treatment patterns among older women result in increased morbidity (e.g., from recurrence), shortened disease-free or overall survival, or decreased quality of life.