Side Effects Could Cause Women To Stop Taking Drugs Aimed At Preventing Breast Cancer Recurrence, Studies Say

Some women taking the drugs tamoxifen and aromatase inhibitors, which block the production of estrogen, to prevent breast cancer recurrence are ending their therapy prematurely because of side effects, according to two studies presented Thursday at the 2007 Breast Cancer Symposium in San Francisco, Reuters reports.

For one study, Alastair Thompson of the University of Dundee in Scotland and colleagues examined the records of 2,080 women treated for breast cancer between 1993 and 2002. The women in the study took tamoxifen for an average of just under 2.5 years to help prevent breast cancer recurrence. Tamoxifen is shown to be most effective if taken for five years, Reuters reports. According to the study, 10% of the women failed to fill 30% or more of their tamoxifen prescriptions. These women were 16% more likely to die during the study period than women who remained on their tamoxifen regimens as directed, the study found. "It could well be a question of side effects," Thompson said, adding, "I think most women who take tamoxifen know that it does have very substantial and life-affecting side effects, even if just hot flashes, which can make life a misery."

In the second study, Lynn Henry of the University of Michigan Comprehensive Cancer Center enrolled 100 women in a trial comparing two different aromatase inhibitors. The study showed that 13% of women taking an aromatase inhibitor requested to be taken off the drug because of muscle aches. Twenty-three percent of the 100 women dropped out of the trial, Henry said. "The vast majority of patients are switching to something else," she said, adding, "They understand that they still need to have their breast cancer treated" (Fox, Reuters, 9/6).

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