Osteoporosis drug may reduce risk of breast cancer?

This article is fresh off the presses. The Women’s Health Initiative, the group that found hormone replacement therapy was bad, has another shocker. Taking an osteoporosis drug reduces the risk of breast cancer by 32%. Here is the hype, er news, in the press release, er article, on reuters:

The analysis from a segment of the more than 150,000 generally healthy post-menopausal women in the WHI study found that those taking Merck & Co’s Fosamax, or other bisphosphonates, had 32 percent fewer cases of invasive breast cancer than women who did not use the osteoporosis medicines, researchers found.

Sounds promising. 150,000 women. 32% fewer cases of breast cancer. That is pretty significant, right? This means instead of 192,000 women getting breast cancer, the rate will reduce to about 127,000 right? No, it does not. Read further:

Studying 2,816 participants who were using bisphosphonates when they entered the WHI program, researchers found that only 64 women developed breast cancer. That translates into 32 percent fewer breast cancers in women using bisphosphonates compared with women who did not use them, researchers said.

Oh, so the entire study was 150,000 women, but only 2,816 were using alendronate. And, of those 64 got breast cancer over the length of the study. This accounts for less than 2.3% of women taking alendronate. Divide that by the number of years of the study (not-mentioned) and you see it is a small number. Since it is a 32% relative risk, this means the absolute benefit from taking alendronate is less than 1 person in one hundred. At numbers this low, we very well might be dealing with a statistical fluke, as we often see these types of rises in numbers when we compare nothing to a placebo in a control group study. Not striking enough for me to put that drug in my body, if I were a woman and did not have Osteoporosis.

But what’s the risk of taking Osteoporosis medicine? In a long term study of alendronate, we find nearly a third of the participants that completed the full study had a serious clinical event during the study, with about 7% with an event serious enough to warrant discontinuation of the study. If we take this to the types of events expected from alendronate (primarily GI), we end up with some where between 15.4% and 30.2% (note that the rates are spread across two dosage groups, which is why there is such a wide spread).

In abosolute terms, less than 1 women out of 100 will benefit from alendronate, as far as breast cancer is concerned, but using the best figures we have, about 15% will experience a serious condition as a result of taking the drug.

Am I stating that alendronate should not be used for women at high risk for cancer? Certainly not. Just that you need to look at both relative and absolute benefit when you are making a decision on what meds to put in your body.

Peace and Grace,

Twitter: @gbworld


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