Regular aspirin may lower colon cancer risk in men
Higher than usual dose of aspirin may keep men away from colon cancer, according to new research findings. However, the benefit requires the dose to be taken over at least six years. Colon cancer is cancer that starts in the large intestine (colon) or the rectum (end of the colon). Together, they're often referred to as “colorectal cancer”. Colorectal cancer is the third most common form of cancer in men.
According to the American Cancer Society, colorectal cancer is one of the leading causes of cancer-related deaths in the United States. There is no single cause for colon cancer. Nearly all colon cancers begin as benign polyps, which slowly develop into cancer. Regular screening tests can help prevent colon cancer by identifying polyps before they become cancerous. If signs and symptoms of colon cancer do appear, they may include changes in bowel habits, blood in your stool, persistent cramping, gas or abdominal pain.
"Long-term data on the risk of colorectal cancer according to dose, duration, and consistency of aspirin therapy are limited," Dr. Andrew T. Chan, of Massachusetts General Hospital, Boston, and colleagues write in the medical journal ‘Gastroenterology’.
The research team went on to collect data on aspirin use and cancer risk factors every two years among more than 47,000 men from 40 to 87 years old at enrollment in the Health Professionals Follow-up Study in 1986. During long period of 18 years of follow-up, 975 cases of colorectal cancer were documented.
According to the researchers, the benefit related to aspirin use was related to the dose of aspirin. Men who used at least two aspirin a week, classified as regular users, had lower risk of colorectal cancer overall than men who did not regularly take aspirin in multivariate analysis controlling for other colorectal cancer risk factors (relative risk 0.79, 95% confidence interval 0.69 to 0.90).
The benefit rose with growing dose (P=0.004 for trend). Compared with men who did not take aspirin, the relative risk of colorectal cancer remained:
- Not reduced for those who took the equivalent of 0.5 to 1.5 standard tablets (325 mg) of aspirin a week (RR 0.94, 95% CI 0.75 to 1.18)
- Reduced, but not significantly so, for men taking two to five tablets a week (RR 0.80, 95% CI 0.63 to 1.01)
- Significantly reduced for men taking six to 14 standard aspirin tablets a week (RR 0.72, 95% CI 0.56 to 0.92)
- Dramatically reduced for men who took more than 14 tablets a week (RR 0.30, 95% CI 0.11 to 0.81)
However, use conferred a benefit only for men who reported consistent use for more than five years (P=0.008 for trend).
Greater benefits for longer duration of use were seen for advanced-stage cancers (P=0.03 for stage 2 and P=0.005 for stage 3 and 4 for trend), but not for early-stage cancers (P=0.31 for trend).
When men discontinued regular aspirin use, the benefit fizzled out after four to five years and their relative risk of colorectal cancer was as if they had never taken it (RR 1.00, 95% CI 0.72 to 1.39).
In an accompanying editorial, Peter Lance, M.D., of the Arizona Cancer Center in Tucson, agreed that despite much effort over two decades no chemopreventive intervention for colorectal cancer has yet entered routine clinical practice as part of usual care for healthy members of the general population.
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