Adherence, Clinical Benefits, and Adverse Effects of Endocrine Therapies Among Women with Nonmetastatic Breast Cancer in Developing Countries: A Systematic Review and Meta-analysis

Background: Despite significant advances in breast cancer control and survival with endocrine therapies (ETs), treatment utilization and outcomes in developing countries have not been adequately explored. This review evaluated ET adherence, potential benefits, and harms in populations across developing countries.

Methods: A literature search was conducted through August 2023 in five databases: PubMed, Cochrane Library, Web of Science, Global Health, and WHO Global Index Medicus. Retrieved records were screened to identify observational research presenting at least one outcome in women with nonmetastatic breast cancer in developing countries who received ET (tamoxifen or aromatase inhibitors). A random effects model was used to compute the rates of adherence, discontinuation, adverse events (AEs), disease progression, and death.

Results: A total of 104 studies met the inclusion criteria. Risk of bias was low in most studies, and a large portion of the patients involved Asians. The overall heterogeneity between studies was partially attributed to variations in study design or outcome measurement method. Results showed a pooled adherence rate of 75% (95% confidence interval [CI], 67%-81%) and a discontinuation rate of 16% (95% CI, 10%-25%). Treatment side effects and young age consistently emerged as significant predictors of nonadherence. A wide range of AEs was identified in our analysis. The estimated average rates of cancer recurrence and mortality at 5-years were 16% and 8%, respectively.

Conclusions: The findings of this study underscore suboptimal ET use in developing countries and provide comprehensive insights into treatment experiences in the real-world setting. Targeted strategies are warranted to enhance adherence and subsequently optimize treatment benefits.