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Small intestinal cancer is a rare form of the disease. The average five-year survival rate for early-stage patients is about 80%, but it drops to only 40% for late-stage cases. Despite continuous efforts by the medical community to research small intestinal cancer and push for early detection, there is a lack of global epidemiological data to help them understand the specific patterns and prevalence of the disease. The Chinese University of Hong Kong (CUHK)’s Faculty of Medicine (CU Medicine) has conducted a study with the Association of Pacific Rim Universities (APRU) to investigate the global distribution, risk factors and epidemiological trends of small intestinal cancer. The results showed that the incidence of small intestinal cancer has also substantially increased globally and the number of new cases in Hong Kong has doubled in the past decade.

The study also found the incidence of small intestinal cancer was higher in high-income jurisdictions, and was closely related to per capita gross domestic product (GDP) levels, the human development index (HDI), and the prevalence of unhealthy lifestyle habits, metabolic diseases and inflammatory bowel disease (IBD) at the country level. The researchers recommend that risk factor control and early cancer detection should be implemented for high-risk populations to mitigate the rise in small intestinal cancer. Details of the study have been published recently in the top international medical journal Gastroenterology.

Hong Kong has the world’s highest small intestinal cancer incidence, with the number of cases doubling in the past decade

Small intestinal cancer’s common symptoms include abdominal pain, loss of appetite, gastrointestinal bleeding, weight loss, small intestine perforation, intestinal obstruction and obstructive jaundice. Due to the challenges of detecting it, small intestinal cancer is often diagnosed at an advanced stage when it has already metastasised, resulting in relatively poorer treatment outcomes.

Currently, the crude incidence rate of small intestinal cancer in Hong Kong is 2.2 cases per 100,000 individuals, with an age-standardised incidence rate of 1.0. These rates indicate a relatively high incidence compared to the global average. According to data from the Hospital Authority, the number of new cases of small intestinal cancer in Hong Kong has nearly doubled over the past decade, from 88 cases in 2011 to 164 in 2020. There is also an upward trend in the number of deaths, rising from 38 cases in 2011 to 60 in 2020.

Developed regions such as North America, Oceania and Northern Europe have the highest incidence

The research team retrieved data about cancer incidence and the prevalence of different risk factors from international databases such as the Global Cancer Observatory, Cancer Incidence in Five Continents Plus and Global Burden of Disease. They found that the disease burden of small intestinal cancer varied across regions, with North America, Oceania and Northern Europe having the highest incidence (see details in Table 1). In addition, the disease burden of small intestinal cancer was proportional to GDP, HDI and the prevalence of smoking, alcohol consumption, unhealthy diets, physical inactivity, obesity, diabetes, lipid disorders and IBD. This implies that a country or region with a higher level of those risk factors will have higher morbidity from small intestinal cancer.

Global small intestinal cancer incidence is showing an upward trend, with the highest increase observed in elderly patients

Small intestinal cancer incidence has been substantially increasing globally over the past decade, with the highest increase observed in the older population. Using the “Average Annual Percentage Change (AAPC[1])” for comparison, the largest increase in incidence rate among people aged 50 or above was found in Poland, followed by India and Thailand (see details in Table 2).

Dr Jason Huang Junjie, the first author of the study and Research Assistant Professor from The Jockey Club School of Public Health and Primary Care at CU Medicine, said, “The incidence of small intestinal cancer varies by region, which may be associated with differences in healthcare standards, lifestyle habits, metabolic disorders and the prevalence of IBD. Our study provides the most up-to-date and comprehensive evidence on the global distribution, risk factors and trends of small intestinal cancer. Policymakers in different regions should implement evidence-based, targeted prevention strategies to control the relevant risk factors.”

Professor Martin Wong Chi-sang, the senior corresponding author of the study, from The Jockey Club School of Public Health and Primary Care at CU Medicine, added, “Genetic factors account for only about 20% of small intestinal cancer cases. The global incidence rate of small intestinal cancer is increasing, likely due to the rise in environmental risk factors, and improved medical diagnostics leading to higher detection rates. Future studies should explore the reasons behind these epidemiological transitions, so that they can provide insights on the cause and prognosis.”

[1] AAPC is a measure of the overall changes in cancer incidence for a specific period. For example, if the incidence AAPC of a certain cancer in a country is five for the past 10 years, it means that the incidence in that country increased 5% on average each year over the 10-year period.