SAN FRANCISCO—Women who failed to take their tamoxifen prescription regularly had an increased risk of death, Scottish researchers reported here at the Breast Cancer Symposium, a meeting cosponsored by the American Society of Breast Disease, American Society of Breast Surgeons, American Society of Clinical Oncology, American Society for Therapeutic Radiology and Oncology, and Society of Surgical Oncology.
“We didn't expect to find any mortality difference because the belief was that patients would take tamoxifen for five years,” explained Alastair Thompson, MD, Professor of Surgical Oncology at the University of Dundee, who led the study. “We felt that the information we give them, both verbal and written, would encourage them to take what many of us would think is a fairly simple one-tablet-a-day, relatively low-side-effect medication.”
It was “actually quite shocking,” he said, to find that compliance was so low and that the impact on mortality was so high.
To determine whether breast cancer patients were compliant with their tamoxifen prescriptions, Dr. Thompson and colleagues took advantage of a 10-digit patient identifier system used in Scotland. The number links demographic data, clinical records, pharmacy records, and death certificates. The researchers used prescription purchase information to calculate the duration and adherence to tamoxifen.
The team identified 2,080 women in the Tayside region of Scotland who were diagnosed with breast cancer between 1993 and 2002, 1,633 (79%) of whom were prescribed tamoxifen.
The median duration of tamoxifen use was shorter than expected at just 2.42 years, compared with the current standard of five years. This abbreviated duration may be in part due to the fact that the current standard was not put in place in the United Kingdom until the mid-1990s, Dr. Thompson said.
Pharmacy records indicated that the median adherence to the prescription was 93%. For women followed for five or more years, only 49% continued therapy for the entire time with no gaps longer than 180 days. Thirty-seven percent of the patients discontinued their tamoxifen altogether.
When the researchers looked at the mortality rate for the 10% of women in the study with lowest compliance—defined as taking less than 70% of their prescription—they found these women had a 16% increased risk of death compared with those who had better compliance—a difference that was statistically significant.
American researchers reported in 2003 a similarly low rate of compliance in the first year of tamoxifen therapy, with only 87% of women being consistent in their prescriptions. However, because they lacked a linkage between prescription information and mortality data, they were not able to assess the impact on patient death rate.
Better Listening about Side Effects
Although the current results highlight the need for physicians to communicate better with patients, Dr. Thompson said the more important lesson might be that physicians need to listen to their patients better about hot flashes or other side effects. “I think part of the answer [to improving compliance] may be addressing the side effect issue,” he said.
These data may have implications for other oral cancer medications. “If this applies to other anticancer drugs, we need to flag our message to all patients: If you are prescribed an anti-cancer drug, please do take it,” he concluded.
Julie R. Gralow, MD, Associate Professor of Medicine at the University of Washington School of Medicine, who moderated a news briefing that included the study, said she agreed with that conclusion.
“If a woman is prescribed a drug, and the clinician and patient have agreed that she is going to take it, it is important that she take it as prescribed,” Dr. Gralow said. “To take it less than two-thirds or three-quarters of the time is not going to give her the same benefit as if she takes it daily.
“A big strength of this study is that they were able to have a sense of compliance based on prescription refills, which is clearly going to give you a somewhat different view of this than just asking a patient how compliant or adherent she is being. This is very important information,” she added.