Decrease in liver cancer incidence rates in Bamako, Mali over 28 years of population-based cancer registration (1987-2015)

BACKGROUND: Primary liver cancer is common in West Africa due to endemic risk factors. However, epidemiological studies of the global burden and trends of liver cancer are limited. We report changes in trends of the incidence of liver cancer over a period of 28 years using the population-based cancer registry of Bamako, Mali. AIM: To assess the trends and patterns of liver cancer by gender and age groups by analyzing the cancer registration data accumulated over 28 years (1987-2015) of activity of the population-based registry of the Bamako district. METHODS: Data obtained since the inception of the registry in 1987 through 2015 were stratified into three periods (1987-1996, 1997-2006, and 2007-2015). Age-standardized rates were estimated by direct standardization using the world population. Incidence rate ratios and the corresponding 95% confidence intervals (CI) were estimated using the early period as the reference (1987-1996). Joinpoint regression models were used to assess the annual percentage change and highlight trends over the entire period (from 1987 to 2015). RESULTS: Among males, the age-standardized incidence rates significantly decreased from 19.41 (1987-1996) to 13.12 (1997-2006) to 8.15 (2007-2015) per 10(5) person-years. The incidence rate ratio over 28 years was 0.42 (95%CI: 0.34-0.50), and the annual percentage change was -4.59 [95%CI: (-6.4)-(-2.7)]. Among females, rates dropped continuously from 7.02 (1987-1996) to 2.57 (2007-2015) per 10(5 )person-years, with an incidence rate ratio of 0.37 (95%CI: 0.28-0.45) and an annual percentage change of -5.63 [95%CI: (-8.9)-(-2.3)]. CONCLUSION: The population-based registration showed that the incidence of primary liver cancer has steadily decreased in the Bamako district over 28 years. This trend does not appear to result from biases or changes in registration practices. This is the first report of such a decrease in an area of high incidence of liver cancer in Africa. This decrease may be explained by the changes and diversity of diet that could reduce exposure to aflatoxins through dietary contamination in this population.