Tamoxifen side effects may affect patient adherence

September 7, 2007

NEW YORK (Reuters) - Side effects cause many breast cancer patients to stop taking tamoxifen as directed, which, in turn, increases the risk of early death, according to the findings of a new report.

Dr. Alastair Thompson of the University of Dundee, Scotland, and colleagues examined the records of 2080 women treated for breast cancer between 1993 and 2002.

Ten percent failed to fill 30% or more of their tamoxifen prescriptions. These women were 16% more likely to die over the study period than women who took tamoxifen as directed, researchers told attendees of the Breast Cancer Symposium meeting in San Francisco.

Although tamoxifen is most effective when taken for 5 years, the women in the study took the drug for an average of just under 2.5 years.

"It could well be a question of side effects," Dr. Thompson told reporters. "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."

"We need to acknowledge that this is something that is truly affecting our patients," Dr. Julie Gralow of the University of Washington School of Medicine said in a telephone briefing.

A second study presented at the meeting found that patients taking an aromatase inhibitor to prevent breast cancer recurrence developed mysterious aches and pains.

Dr. Lynn Henry of the University of Michigan Comprehensive Cancer Center found that 13% of women taking an aromatase inhibitor asked to stop because of muscle aches.

Overall, 23% of 100 women enrolled in a trial comparing two different aromatase inhibitors dropped out because of side effects, Dr. Henry said.

"The vast majority of patients are switching to something else. They understand that they still need to have their breast cancer treated," Dr. Henry told reporters. They may need to switch to another aromatase inhibitor or tamoxifen, she said.

The Breast Cancer Symposium is sponsored by five cancer care societies, including the American Society of Clinical Oncology.