What were the side effects of letrozole?
The most common side effects were hot flashes, sweating, edema, sore muscles and fatigue. Of these, hot flashes and sore muscles were more common in those receiving letrozole than the placebo, but vaginal bleeding was more common in those taking the placebo. Letrozole is already available to treat certain forms of breast cancer and has generally well-tolerated side effects. The side effects seen in this study were consistent with those previously seen. Only 4.5% of women taking letrozole stopped the medication due to side effects whereas 3.6% taking the placebo did so. One concern about lowering estrogen levels over the long term is that it could cause thinning of the bones (osteoporosis) and raise cholesterol levels, leading to more heart attacks. The researchers noted that osteoporosis was diagnosed slightly more frequently among women taking letrozole – 5.7% versus 4.5% on placebo. A separate sub-study in a few hundred women is looking at this question in more detail. The researcher
