ASCO Breast: Women Who Tend to Slip Tamoxifen Have Higher All-Cause Mortality

September 10, 2007

SAN FRANCISCO -- Faithful adherence to adjuvant tamoxifen may be a life-saver for breast cancer patients, researchers said here.

SAN FRANCISCO, Sept. 10 -- Faithful adherence to adjuvant tamoxifen may be a life-saver for breast cancer patients, researchers said here.

Scottish women who filled fewer than 70% of their adjuvant tamoxifen prescriptions were 16% more likely to die (P=0.009) whereas longer duration of use decreased mortality risk by 13% (P

His group retrospectively studied the cohort of all women with incident breast cancer from 1993 to 2002 in a region of Scotland, which gives each citizen a 10-digit identifier that includes their date and place of birth and other demographic information.

The researchers used this code for each of the 2,080 women to link hospital records, prescription records, comorbidity, and socioeconomic status.

Adherence, calculated by summing the filled prescriptions then dividing by duration from first to last prescription, was 93% on average.

About one in 10 women filled fewer than 70% of their tamoxifen prescriptions, Dr. Thompson said. These women had a 16% greater risk of all-cause mortality than those who filled all their prescriptions (95% CI 4% to 30%, P=0.009).

"We don't know whether they're dying as a consequence of not taking the drug or some other reason, but there's a moderately strong statistical association there, which certainly worries me a lot," Dr. Thompson said.

The 21% (447) of women who were not prescribed adjuvant tamoxifen were at greater mortality risk (hazard ratio 1.50, 95% confidence interval 1.16 to 1.94) even controlling for all other covariates.

The difference was not due to differences in tumor stage (P=0.86), but prognosis could have played a role. Patients prescribed tamoxifen were less likely to have positive nodes (P=0.001), metastases (P=0.03), worse tumor grades (P

"If it gives them hot flashes and other not-so-nice side effects then I can't blame people for not wanting to take the tablet every day," he said.

Better communication may be a solution, but the most important feature may be listening to find those who need help with side effects, Dr. Thompson said.