Colorectal cancer incidence trends in Golestan, Iran: An age-period-cohort analysis 2004-2018.

BACKGROUND: We investigated the effects of factors including age, birth year (cohort) and diagnosis year (period) on colorectal cancer (CRC) incidence trends in Golestan, Northeast of Iran, 2004-2018. METHODS: We obtained data on incidence cases of CRC from the Golestan Population-based Cancer Registry by sex and area of residence (urban/rural). Age-standardized incidence rates (ASRs) were calculated using the World standard population and presented per 100,000 person-years. We calculated the estimated annual percentage change (EAPC) with 95 % confidence intervals (95 % CI) fitted age-period-cohort (APC) models to assess non-linear period and cohort effects as incidence rate ratios (IRRs). RESULTS: Overall, 2839 new cases of CRC (ASR = 13.7) were registered in the GPCR over 2004-2018. Our findings suggested significantly increasing trends in CRC incidence rates from 2004 to 2018 (EAPC = 3.7; 95%CI: 0.4, 7.1), with the greatest changes occurring in rural women (EAPC= 4.7; 95%CI: 0.4, 9.2). We observed a strong cohort effect with a consistent increase in the IRR across successive birth cohorts, starting with the oldest birth cohort (1924) (IRR= 0.1 versus the reference birth cohort of 1955) through to the most recent cohort born in 1983 (IRR= 1.9). The largest cohort effects were found among rural females (IRR = 0.0, and IRR = 2.5 for the oldest and the youngest birth cohorts vs. the reference birth cohort, respectively). CONCLUSION: The increasing trends in CRC rates in Golestan are largely driven by generational changes in exposure to underlying risk factors. Further investigations are warranted to deliver effective prevention strategies for the control of CRC in Golestan.

Esophageal and gastric cancer incidence trends in Golestan, Iran: An age-period-cohort analysis 2004 to 2018.

Golestan province in the northeast of Iran is part of the Asian esophageal cancer belt and is known as a high-risk area for esophageal (EC) and gastric cancers (GC). Data on incident cases of EC and GC during 2004 to 2018 were obtained from the Golestan Population-based Cancer Registry (GPCR). The age-standardized incidence rates (ASRs) were calculated and presented per 100 000 person-years. The estimated annual percentage change (EAPC) with 95% confidence interval (95% CI) were calculated. We also fitted age-period-cohort (APC) models to assess nonlinear period and cohort effects as incidence rate ratios (IRRs). Overall, 3004 new cases of EC (ASR = 15.7) and 3553 cases of GC (ASR = 18.3) were registered in the GPCR. We found significant decreasing trends in incidence rates of EC (EAPC = -5.0; 95% CI: -7.8 to -2.2) and less marked nonsignificant trends for GC (EAPC = -1.4; 95% CI: -4.0 to 1.4) during 2004 to 2018. There was a strong cohort effect for EC with a consistent decrease in the IRR across successive birth cohorts, starting with the oldest birth cohort (1924; IRR = 1.9 vs the reference birth cohort of 1947) through to the most recent cohort born in 1988 (IRR = 0.1). The marked declines in EC incidence rates in Golestan relate to generational changes in its underlying risk factors. Despite favorable trends, this population remains at high risk of both EC and GC. Further studies are warranted to measure the impact of the major risk factors on incidence with a view to designing effective preventative programs.