Aspirin in Bowel Cancer

aspirin may prevent bowel cancer by inducing apoptosis in cells undergoing malignant change. Chris Paraskeva, Professor of Experimental Oncology, and Director of the CRC Colorectal Tumour Biology Research Group, the University of Bristol, forecast that Non steroidal anti-inflammatory drugs (NSAIDs) as well as being potentially very important in chemoprevention may also be used in future alongside novel anti-cancer treatments.
One target disease for aspirin is familial adenomatous polyposis (FAP). Inheriting a single mutation for FAP in one gene leads to a near 100% risk of colonic adenocarcinoma.

The evidence that aspirin and (NSAIDs) may prevent cancer is epidemiological, experimental and clinical. In most of the studies (more than 17) published since 1991 aspirin reduced the incidence of colonic polyps or colorectal cancer, the relative risk (RR) in patients ranging from 0.5 to 0.8.

Some carcinogenic gene mutations increase cell proliferation, some prevent apoptosis, yet others increase cell invasion into other tissues. In experimental models NSAIDs restrict colorectal cell proliferation and inhibit tumour vasculature formation by blocking angiogenesis. The Bristol group added salicylate to benign and malignant colonic tumour cells: apoptosis was stimulated in both groups of cells, the carcinoma cells being more sensitive to the salicylate than the non-malignant cells.

aspirin’s effect on prostaglandin synthesis may also be important. Many tumour cells contain high levels of prostaglandins, and aspirin may inhibit their production, with the potential to block many other biochemical pathways. Cyclo-oxygenase, itself blocked by aspirin, may produce carcinogenic compounds.

The current Newcastle trial is using aspirin in FAP to see if it will reduce polyposis. In CAPP2, the hereditary non-polyposis colon cancer study, aspirin and dietary changes will be compared in their effects on tumour development. American experimental data support the epidemiological data: the British clinical data will soon be forthcoming.

Box 2. aspirin 300mg daily lowers cancer rates by between a fifth and a half in patients with familial polyposis coli. It may do so by inducing apoptosis in cells undergoing malignant change. Non-polypotic bowel cancer may also respond to aspirin: trials are under way to test this.