The Association Between Guideline-concordant Care and Risk for Breast Cancer and Non-breast Cancer Mortality Among Older Women with Breast Cancer

Abstract

The purpose of this study is to determine how receipt of guideline-concordant care (GCC) is associated with breast cancer-specific mortality (BCSM) and non-breast cancer mortality (NBCM) among older women with breast cancer. The SEER-Medicare data was used to identify 142, 433 women age > 66 diagnosed with stage I-III breast cancer between 2007-2011. Receipt of GCC was determined according to evidence-based treatment guidelines. Cause-specific Cox proportional hazard multivariable regression models were used to estimate the association between GCC and the risk of BCSM, considering NBCM as a competing event, and NBCM, considering BCSM as a competing event, within five years of diagnosis or until end of follow-up. Among older women with breast cancer, 6.5% experienced BCSM and 11.9% experienced NBCM. GCC was associated with a 24% decreased risk of BCSM (AHR, 0.76; 95% CI, 0.71-0.82), but a 80% increased risk of NBCM (AHR, 1.80; 95% CI, 1.70-1.92). Receipt of adjuvant endocrine therapy was associated with an increased risk of BCSM and a decreased risk for NBCM. Receipt of chemotherapy was associated with an increased risk for BCSM and NBCM, while radiation therapy was associated with a decreased risk of NBCM. Women with a pre-existing dementia, arthritis, hypertension, stroke and increased comorbidity burden had an increased risk for BCSM. Most older breast cancer patients do not receive GCC, yet relatively few die from breast cancer. While GCC does decrease the risk of BCSM, the decision to treat should be made considering the patients existing health status, given that pre-existing comorbidity increases the risk for both BCSM and NBCM. Mortality differences associated with specific types of treatment may be attributed to patient selection for treatment based on worse cancer prognostic factors.