OBJECTIVES: This systematic review and meta-analysis evaluated adherence to endocrine therapies among women with non-metastatic breast cancer in developing countries, a critical issue given the observed challenges in more affluent nations. The study consolidates existing data on utilization patterns and adherence factors.

METHODS: A search for peer-reviewed observational studies was performed from June through August 2023 in five databases including PubMed, Cochrane Library, Web of Science, Global Health, and WHO Global Index Medicus. Two researchers independently conducted the search, screened abstracts and full-text of retrieved studies, extracted data from each eligible article and assessed their methodological quality. A random effects model was used to compute the overall adherence rate, and outcome was plotted as proportions with the corresponding 95% confidence intervals.

RESULTS: Out of 4,146 records identified from the search, 32 studies were included in the current analysis. Most studies used good methodologies based on appraisal criteria and were predominantly from middle-income countries. There were discrepancies across studies in adherence definition, measurements, and assessment methods. Adherence was mainly assessed objectively by pharmacy refill records or subjectively through patient-reporting. Results showed a pooled adherence rate of 75% that ranged from 67% to 81%, indicating non-adherence in 25% of patients on average. Additionally, 16% (95% CI, 10%-25%) of women discontinued treatment early. Patient age and treatment side effects were consistently reported as significant predictors of non-adherence behavior.

CONCLUSIONS: These findings highlight the prevalence of suboptimal adherence to endocrine therapies in developing countries. Targeted strategies to enhance adherence practices are warranted especially in light of the limited resources and high death rates associated with breast cancer in these settings.