Specialty Pharmacy Improves Adherence to Imatinib
Published Online: December 05, 2013
Jay Visaria, PhD, MPH; Rochelle Henderson, PhD, MPA; and Sharon Glave Frazee, PhD, MPH
Chronic myeloid leukemia, also called chronic myelogenous leukemia (CML), is a slow-growing cancer of the white blood (myeloid) cells in bone marrow and blood. It is estimated that there will be 5920 new cases of CML and 610 deaths due to CML in the United States in 2013. The incidence of CML increases with age, with half of all new cases of CML diagnosed in individuals 65 years or older.1 As record numbers of American baby boomers (born between 1946 and 1964) reach their mid-60s, the number of new patients diagnosed with CML is expected to increase.2
Untreated, CML takes an average of 4 years to become more aggressive and reach the blastic stage, when it is usually fatal. However, the prognosis and survival of CML patients have improved dramatically since imatinib, an orally administered chemotherapeutic agent, was approved by the US Food and Drug Administration in 2001. Five-year survival rates for newly diagnosed patients with CML increased from 40% between 1996 and 2000 to more than 55% between 2001 and 2007.3 Long-term studies have shown dramatically decreased mortality and improved survival among CML patients taking imatinib.4,5 Consequently, CML has effectively been transformed into a chronic disease with patients using imatinib and other CML medications over extended periods of time.6 Despite imatinib’s life-extending benefits, many patients struggle to remain adherent to it. A large body of scientific evidence has demonstrated that optimum outcomes from drug therapy are reliant on adherence.7 Although previously published studies have defi ned optimum adherence to imatinib as 90% or above, actual average adherence among US commercially insured CML patients is reported at about 80%,8,9 with only 54% of patients taking imatinib achieving adherence of 90% or higher.9
CML patients face many challenges influencing their medication adherence, including coordination with physicians and other healthcare providers, managing complex treatment regimens, medication side effects, and healthcare costs. Common side effects of imatinib include diarrhea, muscle cramps, nausea, skin reactions, swelling, and vomiting. More serious adverse effects such as myelosuppression (decreased ability of bone marrow to produce blood cells) and elevated liver transaminase levels (indicative of liver damage) may require treatment interruptions.10 Additionally, with the annual cost of therapy reported to be $92,000 in 2012, the economic burden of imatinib is substantial.11 Couple the clinical challenges with the out-of-pocket drug cost facing cancer patients, and it is not surprising that medication adherence is lower than desired, posing a serious concern to patients, clinicians, and payers.
The need to improve medication adherence among patients using oral oncology medications such as imatinib is widely recognized.12,13 According to a National Comprehensive Cancer Center Task Force, oncology-specific support from specialty pharmacies improves adherence, encourages communication between patients and pharmacists, identifies potential safety concerns, helps prevent unwarranted drug expenditures, and ensures appropriate use of medications.14 Given the suboptimal adherence rates to imatinib therapy, patients given this medication, especially those who are new to imatinib therapy,15 are ideal candidates for therapy-related services commonly provided by specialty pharmacies such as refill reminder programs and oncology care management.12,16
Our hypothesis was that adherence to imatinib would be higher among patients starting a new course of therapy with a specialty pharmacy instead of other dispensing channels. Our study objective was to compare imatinib adherence between patients using specialty pharmacy and those using other dispensing channels.
A claims-based, retrospective study was conducted using de-identified prescription data collected by a large national pharmacy benefi ts manager (PBM) with an in-house specialty pharmacy. Patients receiving imatinib through the specialty pharmacy had access to supportive services designed to enhance clinical outcomes, increase drug safety, manage side effects, and help patients stay on therapy. Nurses and pharmacists specifically trained in oncology provided education and care management through proactive patient outreach throughout the course of therapy at clinically meaningful intervals. Telephonic prescription refill reminders were timed to be made when the patient’s quantity of imatinib reached a specifi ed level prior to depletion, to ensure an uninterrupted supply of medication.
Pharmacy claims data for the period July 1, 2010, to August 31, 2012, were analyzed. Irrespective of the type of pharmacy or dispensing channel used, the claims data set included all patients for whom the PBM processed claims for oncology drugs. Thus, patients in the study could obtain imatinib from any combination of the inhouse specialty pharmacy, other specialty pharmacies, retail pharmacies, or home delivery pharmacies. Patients who obtained a simple majority of their 30-day adjusted imatinib prescriptions from the PBM’s in-house specialty pharmacy were assigned to the specialty pharmacy group. Patients receiving a majority of their imatinib supply from other channels were assigned to the other pharmacy group. The design of this study was not submitted to an institutional review board, as only de-identified administrative data were used. All regulations related to the Health Insurance Portability and Accountability Act were followed.17
Patient records selected for the study showed at least 1 prescription claim for imatinib (Medi-Span Generic Product Identifier code 21-53-40-35-10) during the index period between January 1, 2011, and August 31, 2011. Analysis was limited to patients new to therapy, defined as patients with no imatinib claims in the 6 months prior to the index imatinib claim. To accurately assess newto-therapy status and postinitiation adherence, study patients were required to be continuously eligible for pharmacy benefits 6 months prior to and 12 months following the index imatinib claim. Medicare and Medicaid beneficiaries were excluded from the analysis since these patients’ pharmacy benefit design is different from that of commercial patients. Patients who paid 100% of the out-of-pocket cost for imatinib were also excluded from the analysis because it was likely that imatinib was not covered by the pharmacy benefi t for these patients. We may not have captured all transactions for patients who paid 100% of their medication cost. These patients may not have used the pharmacy benefit and hence generated no claims. Each study patient was followed for 365 days after the index imatinib claim.
The outcome of interest was optimum imatinib adherence, a dichotomous variable defi ned as a proportion of days covered (PDC) of 90% or higher during follow-up. The PDC was calculated as the number of days the patient had medication on hand during the 365-day followup period divided by 365.18,19 When the days of supply from a new fill overlapped the last 7 days of supply of imatinib from a previous fill, the fill date for the new fill was adjusted forward to the depletion date of the earlier fill. The patients were thus credited for finishing the supply of imatinib from the previous fill before using the supply of imatinib from the subsequent fill. In situations where multiple claims for imatinib representing different drug strengths (100 mg and 400 mg) occurred concurrently on the same fill date, it was assumed that medication from both claims would be used concurrently and no adjustment was made. The PDC was also evaluated as a continuous variable.
A literature review identifi ed adherence channel confounders, which were included in multivariate analysis. Demographic confounders included patient sex and age at the time of the index imatinib claim.8,9,20,21 Because urbanicity may impact access to pharmacies and therefore adherence,21 we created a dichotomous indicator for whether the 5-digit zip code of the patient’s residence was inside the urban center of a US Census–defined Core Based Statistical Area.22 Patient out-of-pocket cost burden was determined by averaging the amounts paid by the patient (copayment, coinsurance, and deductible) per 30-day supply of imatinib during the follow-up period.20,21 A proxy for patient medication burden9 was the number of therapy classes (as established by the number of unique 2-digit Medi-Span Generic Product Identifi er codes) used by the patient during the follow-up period.21 Because the use of more days of supply per prescription may also improve adherence,23 the average number of days of supply per unadjusted imatinib prescription was included as a covariate. Finally, an indicator was created to identify patients who had at least 1 imatinib claim paid by a plan sponsor whose pharmacy benefit design included a days-of-supply optimization program for specialty medications including imatinib.
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