For sample size calculations, the investigators considered different scenarios based on the published literature and unpublished data. The prevalence of high grade dysplasia in the general population of Golestan has been estimated to be 1.4-3.6%. The sensitivity of cytological detection of esophageal squamous dysplasia (ESD) was predicted to be about 46% based on studies from China, and 60-100% based on studies from Iran, and according to previous studies, 27-65% of ESD lesions progress to invasive ESCC without treatment. The investigators used a rather conservative assumption to calculate sample size: a dysplasia prevalence of 1.5%, a 60% sensitivity for the sponge cytology, and a 2% progression to invasive ESCC in the screened (and treated) group vs. 40% in the untreated group. The investigators also assumed a power of 90%, a mean cluster size of 28 based on the PolyIran study (CV=0.84%), and an intra-class correlation (ICC) of 0.01. Based on these assumptions the investigators will need 4980 people in each arm. So, the investigators need to enroll 9,960 GCS participants > 50 years old. Estimating a 20% lack of consent, the final invitation lists of NESP project will consist of 12000 GCS participants including 6000 subjects in the intervention (capsule sponge) arm and 6000 subjects in the control arm.