Hormone replacement is a difficult and emotional subject, and researchers have made it more complex with findings that women who took hormone replacement were about 1/3 less likely to develop colon cancer.

This was a large observational study, meaning they weren't specifically looking to find such an association. Still, I always look at the magnitude of benefit and the statistics. As a friend once said, I like to see the p-value.

In this case, the statistics (if they can be believed, you know what Twain said), suggest a nice correlation between recent hormone replacement use and less colon cancer.

To put the 36% number in perspective, FDA approved tamoxifen for women at high risk of getting a breast cancer, and that benefit we know is 50% reduction in breast cancer incidence. So, my thinking goes, if we will use tamoxifen, with all of its other problems, to prevent breast cancer in high-risk women then wouldn't we consider using hormone replacement therapy for colon cancer prevention? I don't think there is a lot of mainstream support for the idea, but I'm just asking.

The foregone conclusion is that nobody is going to recommend HRT for colon cancer prevention--but a 36% number doesn't come around every day in cancer prevention. For example, the PCPT found that men were 25% less likely to get prostate cancer if they took Finasteride. Though Merck didn't pursue an FDA approval for Finsteride in prostate cancer prevention, the issue of whether men should take Finasteride for prostate cancer is still hotly debated. That study, the PCPT, was randomized, while the current HRT study for colon cancer was not.

Probably what we need is a randomized trial looking at an HRT intervention and colon cancer outcomes, though we probably won't get this. My main message here is that you have to take these results in the context of prior chemoprevention studies, and if you do, you'll see the data are pretty favorable, if preliminary.

http://www.reuters.com/article/idUSTRE6134XJ20100204