Association of guideline-concordant initial systemic treatment with clinical and economic outcomes among older women with metastatic breast cancer in the United States

Ami Vyas, University of Rhode Island
Tyler Mantaian, University of Rhode Island
Shweta Kamat, University of Rhode Island
Sobha Kurian, West Virginia University School of Medicine Morgantown
Stephen Kogut, College of Pharmacy


Purpose: We examined guideline-concordant initial systemic treatment among women with metastatic breast cancer, its predictors, and if guideline-concordant treatment was associated with mortality, healthcare utilization and Medicare expenditures. Methods: This retrospective observational cohort study was conducted using the Surveillance, Epidemiology, End Results-Medicare linked database. Women aged 66–90 years diagnosed with metastatic breast cancer during 2010–2013 (N = 1282) were included. The National Comprehensive Cancer Network treatment guidelines were used to determine the guideline-concordant initial systemic treatment following cancer diagnosis. A logistic regression analysis was conducted to examine significant predictors of guideline-concordant treatment. Generalized linear regressions were used to examine the association between guideline-concordant treatment and healthcare utilization and average monthly Medicare expenditures. Results: About 74% of the study cohort received guideline-concordant initial systemic treatment. Women who received guideline-concordant treatment were significantly more likely to be comparatively younger (p < 0.05), were married/partnered (p = 0.0038), had HER2 positive tumors, and had good performance status. Adjusted hazards ratios for all-cause (2.364, p < 0.0001) and breast-cancer specific mortality (2.179, p < 0.0001) were higher for women who did not receive guideline-concordant treatment. Rates of healthcare utilization were also higher for women not receiving guideline-concordant treatment. Average monthly Medicare expenditures were 100.4% higher (95% confidence interval: $77.3%–126.5%) for women who did not receive guideline-concordant treatment compared to those who received guideline-concordant treatment (p < 0.0001). Conclusion: One fourth of the study cohort did not receive guideline-concordant initial systemic treatment. Guideline-concordant initial treatment was associated with reduced mortality, and lower healthcare utilization and Medicare expenditures in women with metastatic breast cancer.