Descriptive Epidemiology of Early-Onset Gastrointestinal Cancers in Iran, 2014-2018.

Background: We aim to present incidence rates and geographical distribution of most common early-onset gastrointestinal cancers (EOGICs), including early-onset esophageal cancer (EOEC), gastric cancer (EOGC) and colorectal cancer (EOCRC) in Iran, 2014-2018.

Methods: Data on new cases of EOEC, EOGC and EOCRC were obtained from publicly available annual reports of the Iranian National Population-based Cancer Registry (INPCR). Incidence rates were calculated using the population data available from the Statistical center of Iran. We considered the World standard population for calculation of age-standardized incidence rates (ASR). We also calculated 95% confidence intervals (CIs) for ASR. All rates are presented per 100000 person-years.

Results: Overall, 19,679 new cases of EOGIC were registered by the INPCR between 2014 and 2018. The ASRs (95% CI) of EOEC, EOGC and EOCRC were 0.49 (95% CI: 0.47-0.51), 1.67 (1.63-1.71), and 3.07 (3.01-3.13) per 100,000 person-years, respectively. Our findings indicate decreasing and constant trends in the ASR of EOEC and EOGC during the study period, 2014-2018. There was an increasing trend in the ASR of EOCRC. We also found geographical disparities in the incidence rates of EOGICs across provinces of Iran, suggesting the highest ASRs of EOEC in Golestan (1.3), EOGC in Ilam (2.99) and EOCRC in Ilam (4.49).

Conclusion: Our findings suggested that the incidence rate of EOCRC is consistently increasing. We also found variations in the incidence of EOGICs among different provinces. Further investigations are recommended to clarify the time trends and risk factors of EOGICs in Iran.