Demographic and clinical factors associated with cardiovascular events in elderly long-term survivors of breast cancer.

Abstract

e24105 Background: Improvements in cancer-specific survival have led to a growing appreciation for non-cancer drivers of mortality, particularly cardiovascular disease (CVD), in long-term cancer survivors. However, studies of population-level, non-oncologic outcomes in long-term survivors as a function of treatment exposures remain limited. Our aim is to evaluate the risk of developing cardiovascular disease (CVD) based on demographic and clinical characteristics in long-term breast cancer survivors, defined as those alive five years after diagnosis. Methods: We conducted a SEER-Medicare retrospective study of patients over age 65 with non-metastatic breast cancer, treated with curative intent surgery, diagnosed between 2003-2011, and enrolled in fee-for-service Medicare. CVD events were defined by the presence of any claims corresponding to stroke, heart failure, myocardial infarction, or cardiomyopathy beginning at 5 years after initial diagnosis and extending through year 10. Chi-squared tests were used to examine associations between demographic and clinical characteristics and CVD status. LASSO regularization was used for variable selection in a cox-proportional hazards model using 10-fold cross validation showing CVD hazard ratios stratified by diagnosis year. Results: 43,347 patients met inclusion criteria, of which 5,444 had a diagnosis of CVD between five years after diagnosis and last follow-up. Compared to patients without evidence of CVD, patients experiencing CVD were more likely to be older, Black, live in impoverished neighborhoods, have stage III (vs. I or II) disease, and have been diagnosed during the latter part of the study period (2009-2011 vs. 2003-2008). Variables included in the model following the LASSO regularization process were age at diagnosis, race/ethnicity, % with poverty, metropolitan residence, cancer stage at diagnosis, receipt of radiation therapy, and diagnosis year. Age, race/ethnicity, and cancer stage at diagnosis were significant predictors of developing CVD during years 5-10 after an initial cancer diagnosis (P < 0.001). Risk of developing CVD increased with age and was associated with a threefold higher risk in women over age 85. Non-Hispanic Black patients were at the highest risk across race/ethnicity groups (HR: 1.48, 95% CI: 1.34 – 1.65), and patients with a stage III diagnosis were at the highest risk by stage (ref Stage I; HR: 1.56, 95% CI: 1.41 - 1.72). Those diagnosed in 2009-2011 were at higher risk of developing CVD than in earlier years (ref 2003-2005; HR: 1.67, 95% CI: 1.56 – 1.79). Conclusions: Age, race, poverty, and cancer stage at diagnosis were associated with increased risk of developing CVD in long-term breast cancer survivors. Patients with elevated non-oncologic risks may benefit from increased participation by primary care as a component of effective cancer survivorship.