Chemoprevention, pharmacological intervention for disease prevention, aims to intervene in pathways that lead to clinical disease before the disease occurs.
Cancer chemoprevention is a relatively new field, but for
gastrointestinal cancers, clinical trials have highlighted the chemopreventive potential of several agents. For colorectal
neoplasia, trials with
aspirin and other non-steroidal anti-inflammatory drugs (
NSAIDS) and
calcium have demonstrated the most significant reductions of risk. In observational studies,
NSAIDs also consistently appear to protect against oesophageal and
gastric cancer.
Calcium, and perhaps
vitamin D, are also promising and have the advantage of being inexpensive, safe interventions. For the prevention of oesophageal
cancer, antitumour-B and
retinamide have provided hopeful results, although it is not clear that these findings can be extrapolated from the study populations in Asia to western countries. Evidence from China suggests that a combination of
beta-carotene,
alpha-tocopherol and
selenium may protect against oesophageal
cancer, but the relative importance of each agent is unclear, and, again, their effects in other populations has not yet been assessed. Mass immunization against
hepatitis B seems to be the most effective means of reducing the incidence of
hepatocellular cancer worldwide. In addition, treatment with
interferon alpha in patients chronically infected with hepatitis C virus shows considerable promise, given the increasing prevalence of hepatitis C virus carriage in recent years.
TJ-9,
polyprenoic acid and anti-
aflatoxin compounds are also possible avenues that deserve future research.