Gastric cancer is a global health threat and contributes to more than 720,000 deaths per year. In the absence of early detection, gastric cancer is associated with a high fatality rate-the 5-year survival rate for patients with locally advanced disease is only about 40% despite aggressive treatment. Carcinogenesis in gastric cancer follows a multistage process (i.e., Correa's model) that develops from chronic active gastritis to atrophic gastritis, intestinal metaplasia, dysplasia, and finally to carcinoma. Helicobacter pylori is now recognized as the main risk factor that initiates this process. An estimated 89% of non-cardiac cancers can be prevented if H. pylori can be eradicated from the population of interest; hence, H. pylori eradication has been considered the most effective method to ameliorate the burden of gastric cancer. However, in the setting of mass screening, irreversible damage may already have occurred after patients have harbored H. pylori infection for decades before they undergo screening and treatment for H. pylori. This observation has been supported by a recent meta-analysis based on 8 randomized controlled trials and 16 cohort studies that investigated the magnitude of the benefit from eradication therapy; on average, only a 50% reduction of gastric cancer risk was shown. Altered levels of serum pepsinogens, which are mainly produced by the chief cells of the fundic glands of the stomach, reflect the atrophic status (ie, gland loss) of gastric mucosa. Serum pepsinogen levels not only reveal the past infection status or current atrophy of the stomach, respectively, but have also been shown to be predictive of gastric cancer risk. Therefore, to completely eliminate the burden of gastric cancer, physicians urgently need a risk prediction model with the combination of H. pylori infection and serum pepsinogen level to identify the highest-risk patients for endoscopic examination in the context of limited resources.

Colorectal cancers (CRC) rank second and third as the leading causes of cancer-related death in men and women, respectively, in the world. To reduce the burden of CRC, colonoscopy is the most effective method and can reduce the risk of new-onset CRCs by the removal of adenomatous polyps and can improve CRC survival by the detection of pre-symptomatic malignancies. In addition to primary screening colonoscopy, a two-stage approach using the fecal immunochemical test (FIT) is increasingly popular because of its ability to identify patients with the highest risk of CRC; in this manner, limited colonoscopist resources can be efficiently allocated. Although colonoscopy is associated with a statistically significant reduction in mortality rates for CRC through the detection of early-stage cancers, the FIT levels may serve as a guide for priority setting in prompting residents to undergo colonoscopy. Besides, the prevalence of any CRC and advanced-stage CRC is associated with delays in follow-up colonoscopies for patients with positive results from a FIT. Therefore, the effectiveness and utility of aggressive referral confirmatory diagnosis protocol in a colorectal cancer screening program for those with high FIT levels urgently need to evaluate.