Trends in the Incidence of Cancers of the GI Tract in Harare, Zimbabwe, 1990-2019

PURPOSE Data on long-term time trends in the incidence of cancer are an invaluable resource for tracking the evolution of the disease in populations, but they are very scarce in Africa. The Zimbabwe National Cancer Registry of Harare can report on the evolution of the cancer epidemic over a 30-year period. METHODS Trends in age-standardized incidence rates in the Black (African) population (males and females) are reported for six cancers of the GI tract (oral cavity plus oropharynx, esophagus, stomach, colon plus rectum, liver, and pancreas). RESULTS There has been a steady increase in the incidence of colorectal cancer, at about 2.5% annually, in both sexes, whereas liver cancer has declined, rather more rapidly in males (3.6% annually) than in females (3% annually). Although the incidence is much lower, cancers of the oral cavity and oropharynx have increased in both sexes (3.5% annually in males, 2.8% [nonsignificant] in females). The incidence of stomach cancer has risen over the period, although significantly so only in the most recent decade (2010-2019), before which there had been a slight decline in rates. While esophageal cancer has declined in incidence in men (1.8% annually), it has increased in women (2.4% annually), with adenocarcinomas comprising an increasing proportion (although still less common than squamous cell carcinomas). There has been no significant trend in the incidence of pancreatic cancer. CONCLUSION While some of these trends are related to population-level changes in lifestyles and exposure to environmental factors (such as hepatitis viruses and aflatoxins), the reasons for other changes in incidence are more obscure. While some may be in part due to improvements in diagnostic techniques (endoscopy and imaging), others merit further investigation.