Association Between Adherence to Clinical Practice Guidelines for Adjuvant Therapy for Breast Cancer and Survival in a Resource-Limited Setting

PURPOSE: Addressing unwarranted clinical variation in oncology practices is expected to lead to improved cancer outcomes. Particularly, the application and impact of treatment guidelines on breast cancer outcomes are poorly studied in resource-limited settings. We measured adherence to a set of locally developed adjuvant treatment guidelines in a middle-income setting. Importantly, the impact of guidelines adherence on survival following breast cancer was determined. METHODS: Data of 3,100 Malaysian women with nonmetastatic breast cancer diagnosed between 2010 and 2017 were analyzed. Adherence to the Malaysian Clinical Practice Guidelines for Management of Breast Cancer second Edition was measured. Outcomes comprised overall survival and event-free survival. RESULTS: Guideline adherence for chemotherapy, radiotherapy, hormonal therapy, and targeted therapy were 61.7%, 79.2%, 85.1%, and 26.2%, respectively. Older age was generally associated with lower adherence to guidelines. Compared with patients who were treated according to treatment guidelines, overall survival and event-free survival were substantially lower in patients who were not treated accordingly; hazard ratios for all-cause mortality were 1.69 (95% CI, 1.29 to 2.22), 2.59 (95% CI, 1.76 to 3.81), 3.08 (95% CI, 1.94 to 4.88), and 4.48 (95% CI, 1.98 to 10.13) for chemotherapy, radiotherapy, hormone therapy, and targeted therapy, respectively. Study inferences remain unchanged following sensitivity analyses. CONCLUSION: Our study findings appear to suggest that adherence to treatment guidelines that have been adapted for resource-limited settings may still provide effective guidance in improving breast cancer outcomes.