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Abstract & Commentary
By William B. Ershler, MD
Synopsis: In a randomly selected population of post-menopausal breast cancer patients treated with either tamoxifen or anastrozole, discordance was found between self-reported adherence to prescribed treatment and actual records of prescription fills provided by local hospital and physician records. The findings support further research in developing strategies to better understand and overcome non-adherence.
Source: Ziler V, et al. Adherence to adjuvant endocrine therapy in postmenopausal women with breast cancer. Ann Oncol. 2009;20:431-436.
Adherence with long-term oral medication for chronic illness is a challenge of increasing importance, particularly as new oral formulations for a variety of cancer types have become available. Certainly, non-adherence is a factor of considerable importance in the explanation of outcomes that are less than desired. In this regard, adjuvant endocrine therapy for early-stage breast cancer is of particular concern because earlier reports have suggested poor adherence to prescribed treatment. For example, previous studies evaluating adherence to tamoxifen (TAM) using self-reported evaluation or database claim methods found adherence rates ranging from 65%-85% at different lengths of follow-up.1-4
The current analysis from Marsburg, Germany was designed to evaluate the rate of adherent patients in a randomly selected sample of post-menopausal women with primary breast cancer who had been assigned to an adjuvant endocrine treatment with TAM or anastrozole (ANA). For this, a random sample of 100 post-menopausal women with breast cancer (50 TAM and 50 ANA) who had received surgery for their primary breast cancer in 2004/2005 and, thereafter, had been assigned to an adjuvant endocrine treatment were evaluated. Adherence rate was determined using both a detailed questionnaire and a retrospective prescription check of hospital and physician records. A patient was counted as adherent with a self-reported tablet intake of 80% or more and if a medication possession ratio of 80% or more was achieved.
Regarding the baseline characteristics, a significant difference in mean age was noticed in women on ANA vs. TAM (65 [± 3 years] and 72 [± 3 years]; p < 0.001). All women on TAM and ANA reported themselves to be adherent (100%). After controlling for prescriptions, only 40 (80%) and 27 (69%) of the women on TAM and ANA, respectively, were still classified as adherent (p < 0.01 and p < 0.01 vs. self-report). There was no significant correlation of adherence to any baseline characteristics or side effects in a logistic regression model.
An important goal of any therapeutic intervention is to achieve comparable efficacy in routine clinical practice, as demonstrated in randomized clinical trials. However, a similar magnitude of adherence will be necessary in routine clinical practice to assure comparable clinical effects. The current results further support the data on suboptimal adherence of women with breast cancer on adjuvant TAM treatment and indicate comparable findings for adjuvant ANA. Physicians need to be aware of adherence issues to explain, as possible, the importance of compliance if the therapeutic goals are to be achieved, and to be prepared with alternative treatments or strategies if it is clear that patients are not adhering to the current treatment plan. More prospective studies are needed to increase our understanding of the underlying reasons for non-adherence, in general, and in women with breast cancer specifically.
1. Partridge AH. Non-adherence to endocrine therapy for breast cancer. Ann Oncol. 2006;17:183-184.
2. Partridge AH, et al. Nonadherence to adjuvant tamoxifen therapy in women with primary breast cancer. J Clin Oncol. 2003;21:602-606.
3. Barron TI, et al. Early discontinuation of tamoxifen: A lesson for oncologists. Cancer. 2007;109:832-839.
4. Demissie S, et al. Adjuvant tamoxifen: Predictors of use, side effects, and discontinuation in older women. J Clin Oncol. 2001;19:322-328.