Utilisation of endocrine therapy for cancer in Indigenous peoples: a systematic review and meta-analysis

Indigenous peoples worldwide experience inequitable cancer outcomes, and it is unclear if this is underpinned by differences in or inadequate use of endocrine treatment (ET), often used in conjunction with other cancer treatments. Previous studies examining ET use in Indigenous peoples have predominately focused on the sub-national level, often resulting in small sample sizes with limited statistical power. This systematic review aimed to collate the findings ofarticles on ET utilisation for Indigenous cancer patients and describe relevant factors that may influence ET use.

We conducted a systematic review and meta-analysis of studies reporting ET use for cancer among Indigenous populations worldwide. PubMed, Scopus, CINAHL, Web of Science, and Embase were searched for relevant articles. A random-effect meta-analysis was used to pool proportions of ET use. We also performed a subgroup analysis (such as with sample sizes) and a meta-regression to explore the potential sources of heterogeneity. A socio-ecological model was used to present relevant factors that could impact ET use.

Thirteen articles reported ET utilisation among Indigenous populations, yielding a pooled estimate of 67% (95% CI:54 - 80), which is comparable to that of Indigenous populations 67% (95% CI: 53 - 81). However, among studies with sufficiently sized study sample/cohorts (≥ 500), Indigenous populations had a 14% (62%; 95% CI:43 - 82) lower ET utilisation than non-Indigenous populations (76%; 95% CI: 60 - 92). The ET rate in Indigenous peoples of the USA (e.g., American Indian) and New Zealand (e.g., Māori) was 72% (95% CI:56-88) and 60% (95% CI:49-71), respectively. Compared to non-Indigenous populations, a higher proportion of Indigenous populations were diagnosed with advanced cancer, at younger age, had limited access to health services, lower socio-economic status, and a higher prevalence of comorbidities.

Indigenous cancer patients have lower ET utilisation than non-Indigenous cancer patients, despite the higher rate of advanced cancer at diagnosis. While reasons for these disparities are unclear, they are likely reflecting, at least to some degree, inequitable access to cancer treatment services. Strengthening the provision of and access to culturally appropriate cancer care and treatment services may enhance ET utilisation in Indigenous population. This study protocol was registered on Prospero (CRD42023403562).