I remember more than 2 decades ago having lunch with a radiation oncologist who specialized in breast cancer therapy. In this early era of prophylactic tamoxifen therapy she said to me, “Debi, all these trials evaluating the impact of tamoxifen on women’s breast cancer, how do we know they actually took the drugs?” I must admit, this was the first time I had ever thought of this.
As health professionals we have historically assumed that every patient takes 100% of their drug, 100% of the time. Yet, numerous historical studies of hypertension, diabetes, and AIDS medication adherence clearly reveal that prescription is not synonymous with ingestion.
Optimal adherence has been defined as a patient taking their medication exactly as prescribed, namely, at the exact time, dosage, and for the recommended length of time.1 It is not necessarily representative of a conscious, unilateral decision to forego medical advice. Rather, it is often a complex phenomenon with cognitive, psychological, social, and financial corollaries.
Adherence is assuming increasing scrutiny in the contemporary world of medical oncology as the number of current and future oral therapies increases. Hence, it is important to disseminate recent results of studies that address this construct.
Pharmacists associated with the Tom Baker Cancer Centre in Calgary reported on their review of dispensing records of patients receiving tyrosine kinase inhibitors for chronic myelogenous leukemia (CML).2 They utilized the medication possession ratio (MPR) which discerns adherence rate by dividing the number of days the medication is supplied, by the number of days between first and last refills.3 An adherent patient was identified as one who took > 90% of the prescribed regimen. Results revealed that that nearly one-third of patients were nonadherent to their tyrosine inhibitor therapy. Of note, is that a major molecular response (MMR) is not observed in CML when adherence is less than 80%.4, 5
Another investigation by Flemish researchers of patient adherence with oral tyrosine kinase inhibitor therapy, aimed to gain insight into processes and factors influencing nonadherent behavior.6
Via patient interviews, results revealed that adherence was influenced by a set of complex, inter-related factors (i.e., presence of toxicities, degree of hope, level of anxiety, trust in the health professionals). Of note, was that patients also addressed the absence of feedback as a factor determining adherence. By this, they described the expectation that they would experience medical symptoms when they were nonadherent. Also, the absence of the cancer care team reinforcing the need for adherence, or down playing the deleterious effects of nonadherence, minimized the patient’s perception of pill-taking importance.
Finally, the authors of a comprehensive review of adherence among patients with hematological malignancies, proposed an “at-risk patient” profile for nonadherence with CML therapy.7 Some of these risk factors included low education level, knowledge deficiency on the impact of their cancer and its therapy, low self-efficacy, high toxicity and complication rates, nonparticipation in a clinical trial, and numerous social characteristics (i.e., low level of social support, living alone, low socioeconomic status).
Also of note was a recent finding in a study of breast cancer patients regarding nonadherence. Investigators found that nonadherence to medications for other noncancer chronic conditions was associated with greater nonadherence to oral adjuvant oral hormonal therapy.8 Hence, a past history of nonadherence may be predictive of levels of adherence within cancer treatment.
Treatment outcomes can be directly related to medication adherence. Nonadherence has also been associated with greater health care utilization and costs.7 Recent reports offer testimony to the ongoing need for interventions to enhance adherence. These include verbal, written, and visual patient instruction, information on side effect management, daily medication reminders to ensure patients conform to medical advice, emotional and social support. In the absence of such, adherence, not necessarily treatment resistance or disease insensitivity, may be the culprit in less than optimum therapeutic outcomes.
- Breccia M, Efficace F, Alimena G. Imatinib treatment in chronic myelogenous leukemia: What have we learned so far? Cancer Lett. 2011 Jan 28;300(2):115-21.
- Anderson KR, Chambers CR, Lam N, et al. Medication adherence among adults prescribed imatinib, dasatinib, or nilotinib for the treatment of chronic myeloid leukemia. J Oncol Pharm Pract. 2015 Feb;21(1):19-25.
- Peterson A, Nau DP, Cramer JA, et al. A checklist for medication compliance and persistence studies using retrospective databases. Value Health. 2007 Jan-Feb;10(1):3-12.
- Marin D, Bazeos A, Mahon F, et al. Adherence is the critical factor for achieving molecular responses in patients with chronic myelogenous leukemia who achieve complete cytogenetic responses on imatinib. J Clin Oncol. 2010 May 10;28(14):2381-8.
- Ganesan P, Sagar T, Dubashi B, et al. Nonadherence to imatinib adversely effects event free survival in chronic phase chronic myeloid leukemia. American Journal of Hematology. 2011 Jun;86(6):471-474.
- Verbrugghe M, Duprez V, Beeckman D, et al. Factors Influencing Adherence in Cancer Patients Taking Oral Tyrosine Kinase Inhibitors: A Qualitative Study. Cancer Nurs. 2016 Mar-Apr;39(2):153-62.A
- Hall AE, Paul C, Bryant J, et al. To adhere or not to adhere: Rates and reasons of medication adherence in hematological cancer patients. Crit Rev Oncol Hematol. 2016 Jan;97:247-62.
- Neugut A, Zhong X, Wright JD, et al. Nonadherence to Medications for Chronic Conditions and Nonadherence to Adjuvant Hormonal Therapy in Women With Breast Cancer. JAMA Oncol. 2016 Oct 1;2(10):1326-1332.