Birth control pills may lower colon cancer risk

Women who have used birth control pills seem to have a slightly decreased risk of colon cancer as they age, a new study suggests.

Researchers found that among nearly 90,000 women ages 40 to 59, those who had ever used oral contraceptives were 17 percent less likely to develop colon cancer over the next 16 years.

The findings are in line with evidence suggesting that estrogen plays a role in colon cancer risk.

Some studies, for example, have found that older women on hormone replacement therapy (HRT) have a lower risk of the disease. In addition, lab experiments have shown that estrogen may inhibit tumor development in the colon by affecting cell growth, or by lowering levels of a cancer-linked hormone called IGF-1.

However, it is too soon to conclude that birth control pills offer colon cancer protection, according to lead researcher Dr. Geoffrey C. Kabat, of Albert Einstein College of Medicine in New York.

It is also possible that there is something else about women who use birth control pills that makes them less susceptible to colon cancer, Kabat explained. They may, for example, be more physically active and weigh less — two factors that studies suggest may lower the risk of colon cancer.

The results are based on 89,835 Canadian women taking part in a study on breast cancer screening that followed them for an average of 16 years. During that time, women who had ever used birth control pills were less likely to develop colon cancer. However, this was not true of women who had used HRT, in contrast to what several previous studies have found.

According to Kabat, there are still “many questions to sort out” regarding hormone use and colon cancer, and the results of any single study have to be interpreted cautiously. More studies are needed, he said, to figure out what factors are important in colon cancer development.

Source: International Journal of Cancer
Source: The Daily Star, August 15, 2009