Poor Adherence to Oral Cancer Drugs a Growing Concern
Chicago, IL—The number of oral oncolytic drugs has increased dramatically, but despite increased convenience, there is growing concern regarding adherence, said Winson Y. Cheung, MD, MPH, Assistant Professor, University of British Columbia Division of Medical Oncology, Vancouver, at a session on adherence at ASCO 2013. “Oral drugs shift the onus of treatment adherence from healthcare providers to patients,” Dr Cheung said.
Cancers at more tumor sites are being treated with oral therapy, and the duration of therapy is lengthening. Adherence is an issue not only with antineoplastic drugs but also with nononcology drugs, he said.
In one study of 169 patients with chronic myelogenous leukemia (CML), only 14% were 100% adherent to a daily regimen of imatinib (Gleevec) over a 3-month period. Although 91% of the prescribed doses were taken, 71% of the patients took less than the dose prescribed, and 15% took more. Suboptimal responses were more likely in patients with a higher mean percentage of missed doses.
Treatment response is related to adherence, noted Dawn L. Hershman, MD, MS, Associate Professor of Medicine and Epidemiology, Columbia University Medical Center, New York. In chronic-phase CML, nonadherence to imatinib adversely affected event-free survival: the 5-year event-free survival rates were 76.7% in adherent patients and 59.8% in nonadherent patients.
Predictors of Nonadherence
Predictors of treatment discontinuation or nonadherence have been identified. Among women with early-stage breast cancer, those aged <40 years had the highest risk of discontinuation of endocrine therapy. Age ≥65 years and the presence of comorbidities were other factors associated with increased rates of discontinuation. Approximately 33% of women with early-stage breast cancer discontinued aromatase inhibitor therapy within 2 years because of an adverse effect; the rate of discontinuation because of musculoskeletal symptoms was 24.3%.
Higher prescription copayments also predict nonpersistence with aromatase inhibitor therapy. Focusing on patients at the highest risk of discontinuation is an effective use of resources, Dr Hershman said.
Other factors that predict cancer drug discontinuation are being single, being nonwhite, and therapy not being administered by an oncologist, said Dr Hershman.
Strategies to Improve Adherence
Improving adherence requires a multifaceted approach that relies on several strategies:
- Patients should be encouraged to call with questions about their regimen
- The regimen should be as simple as possible
- The consequences of missing doses should be explained to the patient. Involving family members and significant others can aid adherence. Simply “asking patients about adherence detects 50% of nonadherence,” she said.
Technology may be a helpful resource for improving adherence. Phone consultation and daily text messaging reminders increased adherence to imatinib from 79.3% to 98.2% in a study of patients with chronic-phase CML. Texting reminders twice a week for 3 years also reduced the rate of discontinuation of anastrozole (Arimidex).
Dedicated nurse managers assigned to patients at high risk for nonadherence, as well as collaborative care models are other potential solutions, said Dr Cheung. Pharmacist-led interventions are also effective, especially in the setting of polypharmacy.
“There is evidence to suggest that the reduction of out-of-pocket expenses improves medication adherence across clinical conditions,” Dr Cheung said. “Compared with other effective interventions that are relatively complex and resource intensive, reducing copayments can potentially improve adherence for large numbers of geographically diverse patients.”
“Overadherence” is an emerging concern in oncology, because patients sometimes believe that “more is better.” It is often overlooked, because most research has focused on underadherence, but the transition to oral oncolytics requires attention from providers and researchers to this new phenomenon.