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. What's new? The incidence of esophageal cancer (EC) and gastric cancer (GC) is notably high in the Golestan province of northeastern Iran. Recent evidence suggests, however, that trends in these cancers may be changing. Here, temporal patterns in EC and GC incidence in Golestan over the period 2004 to 2018 were investigated. Large declining trends in EC incidence rates were observed. The largest changes occurred among men and in areas historically linked to very high EC risk, indicating generational changes in risk exposures. Meanwhile, no significant shifts in GC incidence were detected and overall risk remains high for EC and GC among Golestan populations.