In the Lancet, a new study combining data from four randomized trials of aspirin versus control in both primary and secondary prevention of vascular events evaluated risk of colorectal cancer over 20 years (study). A fifth trial compared doses of aspirin. After combining the data on individuals in these five trials the investigators observed that aspirin use reduced the 20-year risk of colon cancer but not rectal cancer. Risk of cancer was reduced by 25% and colon cancer mortality was reduced by 35%. Similar to previous reports, benefit of aspirin use increased with duration of use indicating that aspirin use operates early in the pathway to colon cancer and leading to long-term therapy as the necessary approach for prevention of colon cancer. This study, in contrast with previous evidence suggests that the benefit for colon cancer prevention is obtained with as little as 75 mg per day.
Importantly, this study separately evaluated colon cancer rectal cancers. We have previously shown that the risk factors for these two cancers sites vary substantially (Wei, Giovannucci et al. 2004). The evidence for aspirin adds further support for strategies to be specific to risk, particularly among those who are at increased risk, as is the case for family history.
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Cuzick, J., F. Otto, et al. (2009). "Aspirin and non-steroidal anti-inflammatory drugs for cancer prevention: an international consensus statement." Lancet Oncol 10(5): 501-507.
Flossmann, E. and P. M. Rothwell (2007). "Effect of aspirin on long-term risk of colorectal cancer: consistent evidence from randomised and observational studies." Lancet 369(9573): 1603-1613.
Glasziou, P. P. and L. M. Irwig (1995). "An evidence based approach to individualising treatment." BMJ 311: 1356-1359.
Gralow, J., R. F. Ozols, et al. (2008). "Clinical cancer advances 2007: major research advances in cancer treatment, prevention, and screening--a report from the American Society of Clinical Oncology." J Clin Oncol 26(2): 313-325.
Wei, E. K., E. Giovannucci, et al. (2004). "Comparison of risk factors for colon and rectal cancer." Int J Cancer 108(3): 433-442.