Wednesday, April 18, 2007; 4:27 PM

NEW YORK (Reuters Health) - Long-term daily use of adult-strength aspirin may modestly reduce the risk of certain cancers, including colorectal, prostate and breast cancer, new research suggests.

Recent findings from the Women's Health Study suggested that the long-term use of low-dose aspirin does not markedly affect cancer risk. However, it was unclear if the regular use of higher doses has a beneficial effect.

As reported in the Journal of the National Cancer Institute, Dr. Eric J. Jacobs, from the American Cancer Society in Atlanta, and colleagues, assessed the anti-cancer benefits of adult-strength aspirin (at least 325 milligrams per day) by analyzing data from more than 145,000 subjects enrolled in the Cancer Prevention Study II Nutrition Cohort.

During a 10-year follow-up period, 10,931 men and 7196 women were diagnosed with cancer, the report indicates. Daily aspirin use for 5 years or longer lowered the risk of cancer by 16 percent in men and by 14 percent in women.

The long-term use of adult-strength aspirin significantly reduced the risk of colorectal and prostate cancer by 32 percent and 19 percent, respectively. Aspirin use was also associated with a 17-percent reduction in the risk of female breast cancer, but the reduction was not statistically significant.

In a related editorial, Dr. Maria Elena Martinez and Dr. E. Robert Greenberg, from the Arizona Cancer Center in Tucson, comment: "It will be important to verify whether the findings from this study, and especially those for breast and prostate cancer incidence, represent a real benefit" or are due to detection biases or other factors that influenced the cancer incidence in this population.

SOURCE: Journal of the National Cancer Institute, April 18, 2007