SAN FRANCISCOOne in five women in a population-based study
of breast cancer patients did not fill all her tamoxifen (Nolvadex)
prescriptions during the first year of adjuvant tamoxifen therapy. The oldest
and youngest patients and nonwhite patients were least likely to adhere to
their tamoxifen regimens.
For the study, adherence was defined as filling prescriptions
for 80% or more of the year covered and nonadherence as filling prescriptions
for less than 80% of the year. "Seventy-seven percent of the women had
greater than 80% of the year covered with filled tamoxifen prescriptions and
were therefore classified as adherent. Twenty-three percent of the women were
considered nonadherent because they had tamoxifen available to them less than
80% of the year," reported Ann Hart Partridge, MD, clinical fellow in
medicine at Dana-Farber Cancer Institute in Boston. The study researchers were
based at that institution and at Brigham and Women’s Hospital in Boston,
although the study participants were residents of New Jersey.
The adherence rate was higher than the rates of 40% to 50% that
have been observed for many chronic drug therapies, Dr. Partridge said.
Overall Adherence High
"The overall level of adherence with tamoxifen is high
compared to other chronic medications," she said. "However, adherence
is relatively low in absolute terms and compared to perception. Over one fourth
of patients missed greater than 20% of doses and may be at risk for inadequate
clinical response because of poor adherence."
Cancer patients were thought to have too much to lose to miss
taking their tamoxifen, Dr. Partridge added, underscoring tamoxifen’s
efficacy in preventing recurrence and death in women with early stage breast
cancer. She urged greater efforts to ensure tamoxifen adherence, especially
among nonwhite populations and patients who are younger than 45 or older than
The study involved 2,378 women over the age of 18 who were
enrolled in New Jersey’s Medicaid and Pharmaceutical Assistance to the Aged
programs. Each filled a first prescription for tamoxifen between 1991 and 1995.
The study traced whether the subsequent prescriptions filled by the women
provided tamoxifen for all 365 days during the first year of treatment.
Excluding women who had an identifiable reason to discontinue therapyfor
example, breast cancer recurrence during the study yeardid not change the
adherence rates substantially.
Some Factors Ruled Out
The researchers ruled out socioeconomic status, use of estrogen
replacement therapy, tumor staging, year of diagnosis, and other adjuvant
therapies as factors in adherence, according to Dr. Partridge. "Women who
had had a mastectomy were less adherent," she said, "and not being
seen by an oncologist in the year prior to beginning tamoxifen therapy was also
associated with poor adherence." She reported that 46% of the women had
seen an oncologist in the year before receiving their first tamoxifen
prescription, and 60% had undergone mastectomy.
The study was the largest to date on the use of tamoxifen or
any oral antineoplastic agent outside of a clinical trial, according to Dr.
Partridge. "Given the growing number of new effective oral agents for the
treatment of cancer," she remarked, ‘‘attention to adherence is