Strategies for prevention of gastrointestinal cancers in developing countries: a systematic review.

Background: Gastrointestinal cancers account for one third of total cancer incidence and mortality in developing countries. To date, there is no systematic synthesis of evidence regarding strategies to prevent gastrointestinal cancers in developing countries. We aimed to provide a systematic overview of studies evaluating strategies for prevention or early detection of the three most common gastrointestinal cancers (gastric, liver and colorectal cancer) in developing countries.

Methods: We searched MEDLINE, Web of Science and WHO Global Index Medicus databases for relevant articles published until October 2016 using combinations of the search terms "gastrointestinal", "digestive system", "gastric", "liver", "colorectal", "cancer", "prevention", "early detection" and "developing country" (including names).

Results: Overall, 73 articles met the inclusion criteria, providing information on short- and long-term outcomes (up to 30 years) from various intervention studies (∼45% randomized). Trials on hepatitis B vaccination consistently showed vaccine efficacy over time and indicated long-term preventive effects on liver cancer incidence that start to become measurable at the population level. Studies on anti- H. pylori treatment suggested a reduction in gastric cancer incidence reaching statistical significance after long-term follow-up, while evidence regarding a preventive effect in persons with precancerous lesions is still inconclusive. The studies regarding colorectal cancer focused on early detection, ∼90% of which were restricted to intermediate endpoints.

Conclusion: In conclusion, there were a number of studies on gastric and liver cancer prevention in developing countries showing promising results after long-term follow-up. Important next steps include pooled meta-analyses as far as possible given the heterogeneity between studies as well as implementation research.