Nonadherence to oral antineoplastic agents is a contemporary and under-researched yet modifiable phenomenon that compromises cancer treatment outcomes. It is multi-factorial in its causes and requires numerous interventions to prevent, minimize, manage and measure it. Thus, it is a complex entity that can impede optimal treatment outcomes, prompt unnecessary hospitalizations, raise costs, and even heighten mortality.1
In older cancer patients, nonadherence is especially important due to the range and intensity of causal factors. Some of these include the presence of polypharmacy, regimen complexity, cognitive impairment, visual and hearing deficits, drug side effects, comorbidities, lack of social support, financial toxicity, and health beliefs. Acknowledging these potential deterrents, the International Society of Geriatric Oncology (SIOG) recently published recommendations to promote adherence.2
Some key definitional distinctions are in order. Medication adherence is defined
as the degree or extent to which the patient conforms to the prescribed drug
regimen with respect to timing, dosing, and frequency.3 Adherence is characterized
by three components: initiation (the first time the patient takes the
initial dose), implementation (degree of conformity to the prescribed
regimen from initiation to the final dose), and discontinuation (end
of therapy).4 Although health care providers often think of adherence being
associated with the patient consuming less than what is prescribed, the phenomenon
of overadherence should be considered as well as it increases the risk of life-threatening
toxicities and treatment intolerance.2
There is no single gold standard for measuring and monitoring patient adherence. Hence, the SIOG recommendations propose that multiple methods be used. These methods include pill diaries, pill counting, electronic medication reminder devices, tracking via pharmacy databases, patient report, and clinical assessment. The 8-item Morisky Medication Adherence Scale (MMAS-8) is a commonly used self-report tool to monitor adherence over the course of treatment; however, its use in oncology settings is limited.2,5 As the future unfolds, evolving technologic methods such as automated text messaging and other alert systems and telephone support by nurses with facetime interaction may become a standard part of follow-up care with oral antineoplastics.
With older cancer patients, drug toxicity is considered the main reason for premature drug discontinuation.6-8 Another SIOG recommendation is to address the early recognition of regimen-specific toxicities and to have an aggressive plan devised for its management. Hence, patient education is a key intervention in optimizing adherence. Pharmacists can proactively help with toxicity prevention by evaluating the patients pre-oncolytic drug regimen with the proposed antineoplastic one for potential drug interactions.
Finally, the SIOG taskforce advised that not all patients may be appropriate candidates for oral cancer therapies. They suggested that patients be evaluated for their motivation, past history of nonadherence to other chronic medications, and whether they have a poor understanding for the treatment rationale and dosing requirements.
As more oral therapies are under investigation and the American population grows older, this issue of medication adherence becomes more relevant and important. Finding solutions now to address this common barrier to optimum cancer care will help reduce the prominence of this phenomenon in the future.
Greer JA, Amoyal N, Nisotel I, et al. A systematic review of adherence to oral antineoplastic therapies. Oncologist. 2016;21:354-76.
Mislang AR, Wildes TM, Kanesvaran R, et al. Adherence to oral cancer therapy in older adults: The International Society of Geriatric Oncology (SIOG) taskforce recommendations. Cancer Treat Rev. 2017;57:58-66.
Osterberg L, Blaschke T. Adherence to medication. N Engl J Med. 2005;353:487-97.
Vrijens B, De Geest S, Hughes DA, et al. A new taxonomy for describing and defining adherence to medications. Br J Clin Pharmacol. 2012;73:691-705.
Morisky DE, Green IW, Levine DM. Concurrent and predictive validity of a self-reported measure of medication adherence. Med Care. 1986;24:67-74.
Jackman DM, Yeap BY, Lindeman N, et al. Phase II clinical trial of chemotherapy-na´ve patients > or = 70 years of age treated with erlotinib for advanced non-small cell lung cancer. J Clin Oncol. 2007;25:760-6.
Putz F, Knippen S, Lahmer G, et al. A model to predict the feasibililty of concurrent chemoradiotherapy with temozolomide in glioblastoma multiforme patients over age 65. Am J Clin Oncol. 2015; doi: 10.1097/COC.0000000000000198.
Wick W, Platten M, Meisner C, et al. Temozolomide chemotherapy alone versus radiotherapy alone for malignant astrocytoma in the elderly: the NOA-08 randomized, phase 3 trial. Lancet Oncol. 2012;13:707-15.