Triple-negative breast cancer prevalence in Africa: a systematic review and meta-analysis

OBJECTIVE: The aggressive triple-negative breast cancer (TNBC) subtype disproportionately affects women of African ancestry across the diaspora, but its frequency across Africa has not been widely studied. This study seeks to estimate the frequency of TNBC among African populations. DESIGN: Systematic review and meta-analysis using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. DATA SOURCES: PubMed, EMBASE, African Journals Online and Web of Science were searched on 25 April 2021. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: We included studies that use breast cancer tissue samples from indigenous African women with sample size of eligible participants ≥40 and full receptor status for all three receptors (oestrogen receptor (ER)/progesterone receptor (PR)/human epidermal growth factor receptor 2 (HER2)) reported. DATA EXTRACTION AND SYNTHESIS: Two independent reviewers extracted data and assessed risk of bias using the modified assessment tool by Hoy et al. (2012) for prevalence studies. A random-effects meta-analysis was performed, and data were pooled using the inverse-variance method and logit transformation. Pooled frequencies were reported with 95% CIs calculated with the Clopper-Pearson method and heterogeneity quantified with I² statistic. GRADE assessed the certainty of the evidence. RESULTS: 1808 potentially eligible studies were identified of which 67 were included in the systematic review and 60 were included in the meta- analysis. Pooled TNBC frequency across African countries represented was estimated to be 27.0%; 95% CI: 24.0% to 30.2%, I²=94%. Pooled TNBC frequency was highest across West Africa, 45.7% (n=15, 95% CI: 38.8% to 52.8%, I²=91%) and lowest in Central Africa, 14.9% (n=1, 95% CI: 8.9 % to 24.1%). Estimates for TNBC were higher for studies that used Allred guidelines for ER/PR status compared with American Society of Clinical Oncology(ASCO)/College of American Pathologists(CAP) guidelines, and for studies that used older versions of ASCO/CAP guidelines for assessing HER2 status. Certainty of evidence was assessed to be very low using GRADE approach. CONCLUSION: TNBC frequency was variable with the highest frequency reported in West Africa. Greater emphasis should be placed on establishing protocols for assessing receptor status due to the variability among studies.