Researchers from Germany have reported that postmenopausal women with localized breast cancer taking adjuvant Arimidex® (anastrozole) for localized hormone receptor-positive breast cancer had a compliance rate of 67%. The details of this study were published in the March 3, 2009 issue of Annals of Oncology.[1]

Several randomized studies have shown that tamoxifen (Nolvadex®) and aromatase inhibitors such as Arimidex administered for five or more years significantly reduce the risk of recurrence in women with localized hormone receptor-positive breast cancer. Previous studies, however, have shown that compliance to adjuvant tamoxifen is less than optimal. In one U.S. study of women over the age of 65 years, compliance to tamoxifen for five years was 69%. Factors associated with poor compliance included early side effects while patients with a positive attitude had better compliance. In a Swiss study, the compliance rate among postmenopausal women prescribed tamoxifen was 67%. This study suggested that compliance was better in women care for by specialists rather than general practitioners. They also observed that 80% of women who were not compliant to tamoxifen because of side effects were compliant with alternative drugs. These authors suggested that with careful follow-up and change of medication, the rate of non-adherence would be reduced to approximately 10%. Researchers from St. Luke’s-Roosevelt Hospital have reported that 37% of women with estrogen receptor-positive localized breast cancer are not compliant with prescribed tamoxifen, resulting in a higher rate of recurrent disease. However, there have been no reports of the compliance of women taking adjuvant aromatase inhibitors for prevention of recurrent breast cancer.

Researchers involved in the current study sought to determine the relative compliance rates of adjuvant tamoxifen or Arimidex. They performed a random sample of 100 women randomly allocated to receive adjuvant tamoxifen or Arimidex. Based on self-reporting, women were deemed compliant if they reported taking 80% or more of their prescribed medication. By this criterion all women were compliant. However, when prescriptions were checked, only 80% of women taking tamoxifen were compliant compared with 67% for women taking Arimidex.

Comments: These data support previous data suggesting poor compliance with adjuvant hormonal therapy in women with breast cancer irrespective of the type of medication. These authors suggest: “More prospective studies are needed to increase our understanding of the underlying reasons for nonadherence in women with breast cancer.” This study also demonstrated the poor reliability of patient-reporting to determine compliance.

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