"We need to understand this better, to give these women as good an outcome as we can," said study lead author Dr. M. Catherine Lee, a clinical lecturer in the department of surgery at the University of Michigan Comprehensive Cancer Center in Ann Arbor, at a Wednesday teleconference.
A second study found that 10 percent of women filled 70 percent or less of their prescriptions for tamoxifen, a drug taken by many cancer survivors to prevent recurrences.
Tamoxifen has been shown to reduce the recurrence of ER-positive breast cancer when used after primary treatment. Women who often skipped tamoxifen had a 16 percent increased risk of death compared to women who filled all their prescriptions, the researchers noted.
Although the study did not look specifically at why women were dropping the treatment, side effects may play a role.
"Most women who take tamoxifen know it can have substantial and life-affecting side effects such as hot flashes, which can make life misery," said Dr. Alastair Thompson, lead author of the study and a professor of surgical oncology at the University of Dundee in Scotland. "It could be that those sorts of side effects we've downplayed in the past are factoring in," he said.
"Taking your pills really matters," added Dr. Julie Gralow, moderator of the teleconference and associate professor of medical oncology at the University of Washington School of Medicine in Seattle.
A third and final study found that 13 percent of women taking aromatase inhibitors -- drugs that inhibit the production of estrogen for ER-positive breast cancer patients -- stopped this treatment due to musculoskeletal side effects such as rotator cuff tendonitis, carpal tunnel syndrome and osteoarthritis.
Overall in the trial, 42 p
All rights reserved