Chronic inflammation, through a variety of mechanisms, plays a key role in the occurrence and development of digestive system malignant tumors (DSMTs). In this study, we feature and provide a comprehensive understanding of DSMT prevention strategies based on preventing or controlling chronic inflammation. The development and evaluation of cancer prevention strategies is a longstanding process. Cancer prevention, especially in the early stage of life, should be emphasized throughout the whole life course. Issues such as the time interval for colon cancer screening, the development of direct-acting antiviral drugs for liver cancer, and the Helicobacter pylori vaccine all need to be explored in long-term, large-scale experiments in the future.

Morbidity and mortality from hepatocellular carcinoma (HCC), which is primarily caused by hepatitis B virus or hepatitis C virus, can be prevented. Public health interventions have eliminated transfusion transmission of these viruses and, in endemic countries with effective hepatitis B virus vaccination programs, have greatly reduced incident hepatitis B virus infections (and HCC) in children. Antiviral treatment can eliminate detectable hepatitis C virus in 50%-80% of chronically infected patients, presumably reducing their risk of cancer. HCC survival rates remain universally poor, but early detection and treatment in developed countries has improved survival in selected patients. Despite these advances, worldwide HCC rates remain high, and additional preventive efforts are needed. The most important opportunity is wider distribution of hepatitis B virus vaccine in endemic areas. Development of an HCV vaccine, improved antiviral therapies, and better methods for HCC detection would also help decrease morbidity and mortality from HCC. HCC prevention efforts provide a paradigm for preventive oncology in cancers of viral etiology.

The Gambia Hepatitis Intervention Study (GHIS) was initiated by the International Agency for Research on Cancer (IARC) in 1986. It consisted of a randomized trial in the Gambian population, aiming to evaluate the protection provided by HBV vaccination administered during the first year of life against primary infection, the development of chronic carriage, and primary liver cancer. The results, reported at 9 years from the introduction of the vaccine as conferring a high degree of protection (83% against primary infection and 95% against chronic carriage), are briefly discussed. It is expected that HBV vaccination will result in a reduction of mortality from hepatocellular carcinoma, the most frequent cancer in males in sub-Sahara Africa.

Epidemiological studies have clearly shown a causal association between tobacco exposure and various human cancers, hepatitis B and C infection and hepatocellular carcinoma, human papilloma viruses and cervical cancer, and the occupational origin of certain human cancers is well established. The identification of the environmental causes of human cancers has been a long and difficult process. Much remains to be understood about the role of specific components of the diet and the interaction of different risk factors in the aetiology of human cancers. Withstanding the progress made on the understanding of the cancer process and their potential impact in the therapy of cancer, primary prevention remains, in developed and developing countries, the most effective measure to reduce cancer mortality.

Experimental and epidemiological evidence has established an association between at least eight viruses and various cancer sites. Recent estimates (at least 10% of cancer worldwide) have revealed that viruses, together with tobacco and diet, account for the largest proportion of cancer in the world.

Improvements in the detection of viruses and biomarkers of chronic infection have led to the identification of strong associations with cancer, particularly for human papillomavirus (HPV), hepatitis B virus (HBV), and human immunodeficiency virus (HIV). For some cancer viruses (e.g., HIV and hepatitis C virus, HCV), the spectrum of malignancies involved has still to be well defined. For HBV and HPV, vaccination aimed at cancer prevention is already a reality or a possibility. Whereas HBV vaccination already emerged as one of the most cost-effective ways to reduce adult cancer mortality, for HPV vaccination some technical problems still await a solution. For other infectious agents (e.g., HCV, HIV) prospects for a vaccine are not immediate.

In order to apply new knowledge on viruses to cancer prevention, large vaccination trials are warranted. These will have to be large (many thousands of people), prolonged (5-10 years), and match scientific excellence with a feasible design. Mistrust between scientists and the public will have to be prevented by means of absolute openness in scientific information and economical interests involved.