Esophageal cancer male to female incidence ratios in Africa: A systematic review and meta-analysis of geographic, time and age trends

Abstract

Esophageal squamous cell carcinoma (ESCC) remains the predominant histological subtype of esophageal cancer (EC) in many transitioning countries, with an enigmatic and geographically distinct etiology, and consistently elevated incidence rates in many Eastern and Southern African countries. To gain epidemiological insights into ESCC patterns across the continent, we conducted a systematic review and meta-analysis of male-to-female (M:F) sex ratios of EC age-standardised (world) incidence rates in Africa according to geography, time and age at diagnosis. Data from 197 populations in 36 countries were included in the analysis, based on data from cancer registries included in IARC's Cancer Incidence in Five Continents, Cancer in Africa and Cancer in Sub-Saharan Africa reports, alongside a systematic search of peer-reviewed literature. A consistent male excess in incidence rates overall (1.7; 95% CI: 1.4, 2.0), and in the high-risk Eastern (1.6; 95% CI: 1.4, 1.8) and Southern (1.8; 95% CI: 1.5, 2.0) African regions was observed. Within the latter two regions, there was a male excess evident in 30-39 year olds that was not observed in low-risk regions. Despite possible referral biases affecting the interpretability of the M:F ratios in place and time, the high degree of heterogeneity in ESCC incidence implies a large fraction of the disease is preventable, and directs research enquiries to elucidate early-age exposures among young men in Africa.

Keywords: Africa; Esophageal cancer; Meta-analysis; Sex ratios; Systematic review.

Fig. 1

Flow diagram of population inclusion in the different analytical components of the study. Population refers to a group of individuals sharing a common location, period of diagnosis and ethnicity.

Fig. 2

Male-to-female esophageal cancer incidence ratios (y-axis displayed in log scale) plotted against the mid-year of diagnosis, estimated by IRRs (black points) or count ratios (grey points).

Fig. 3

Forest plot of country and region-specific sex ratios estimated using random effects models. Point estimates and their corresponding populations and diagnosis periods are shown in Table 1. *High incidence denotes countries for which the male or female EC ASR exceeds the global EC incidence rate in GLOBOCAN.

Fig. 4

(A) Country-specific estimated age-standardised incidence rates of esophageal squamous cell carcinoma (Arnold et al. [2]) and (B) country-specific sex ratios of esophageal cancer estimated in the present study.

Fig. 5

Forest plot of age-specific sex ratios grouped by region. Estimates were made using random effects models. *High incidence denotes countries for which the male or female EC ASR exceeds the global mean in GLOBOCAN.

Fig. 6

Male-to-female EC ratios plotted against EC ASR in women. Global data (excluding Africa) from CI5 is plotted in comparison to African estimates from the present study. CI5 data are plotted by individual registry and labelled by country.