Why higher copayments for opioids did not reduce use among Medicare beneficiaries.

To examine whether higher cost-sharing deterred prescription opioid use. Medicare Part D claims from 2007 to 2016 for a 20% random sample of Medicare enrollees. We obtain estimates of the effect of cost-sharing on prescription opioid use using ordinary least squares and instrumental variables methods. In both, we exploit the variation (change) in cost-sharing within plans over time for a sample of beneficiaries who remain in the same plan. Focusing on changes in cost-sharing within a plan for a constant sample of beneficiaries mitigates potential bias from plan selection and using a constant set of weights derived from use in year (t) eliminates changes in the cost-sharing indexes due to (endogenous) consumer choice in year (t+1). Part D plans adopted benefit changes designed to reduce opioid use, including moving opioids to higher cost-sharing tiers. Increasing plan copayments for hydrocodone or oxycodone was associated with reductions in plan-paid claims and offsetting increases in cash claims. Widespread availability of low-cost generics combined with the anti-clawback provision in Part D mediated the effect of higher cost sharing to curb opioid use. As plans moved generic opioids to higher cost-sharing tiers, beneficiaries simply paid cash prices and aggregate use remained largely unchanged. The anti-clawback provision in Part D, intended to protect beneficiaries from price gouging, limited plans' ability to constrain opioid use through typical demand-side measures such as increased cost-sharing.

The effect of prescription drug insurance on the incidence of potentially inappropriate prescribing: Evidence from Medicare Part D.

The Medicare Part D program has been documented to increase the affordability and accessibility of drugs and improve the quality of prescription drug use; however, less is known about the equity impact of the Part D program on potentially inappropriate prescribing-specifically, incidences of polypharmacy and potentially inappropriate medication (PIM) use based on different racial/ethnic groups. Using a difference in the regression discontinuity design, we found that among Whites, Part D was associated with increases in polypharmacy and "broadly defined" PIM use, while the use of "always avoid" PIM remained unchanged. Conversely, Blacks and Hispanics reported no changes in such drug utilization patterns.

The Impact of Medicare Low-income Subsidy on Access to Treatment, Treatment Choice, and Oncologic Outcomes in Patients With Metastatic Prostate Cancer.

PURPOSE: Patients eligible for Medicare Part D low-income subsidy have lower cost-sharing for both IV and oral cancer therapies. We evaluated associations between low-income subsidy and treatment choice, treatment initiation, and overall survival in patients with metastatic prostate cancer. MATERIALS AND METHODS: We identified men aged 66 years and older diagnosed with stage IV prostate cancer between 2010 and 2017 included in the Surveillance, Epidemiology, and End Results-Medicare linked data set. Using linear probability models, we evaluated the impact of low-income subsidy on type of first supplementary treatment (oral vs IV) among patients who received nonandrogen deprivation therapy supplementary systemic therapy, and initiation of any nonandrogen deprivation therapy supplementary systemic therapy. Overall survival was estimated with Kaplan-Meier curves. RESULTS: Of the 5,929 patients included, 1,766 (30%) had low-income subsidy. On multivariable analysis, those with low-income subsidy were more likely to receive oral as opposed to IV treatments compared to patients without low-income subsidy (probability difference: 17%, 95% CI 12, 22). However, patients with low-income subsidy were less likely to initiate any nonandrogen deprivation therapy supplementary systemic therapy (oral or IV) compared to those without low-income subsidy (probability difference: 7.9%, 95% CI 4.8-11). Additionally, patients with low-income subsidy experienced worse overall survival than those without low-income subsidy (P < .001). CONCLUSIONS: While low-income subsidy was associated with increased use of more expensive oral therapies in men with metastatic prostate cancer, barriers to accessing these treatments still exist. These findings stress the importance of continued efforts to improve health care access to low-income individuals.

Effects of Medicare Part D coverage gap closure on utilization of branded and generic drugs.

The Affordable Care Act included a provision to gradually eliminate the Medicare prescription drug coverage gap between 2011 and 2020, which substantially lower medication costs in the gap. Using 2007-2016 Medicare claims data, we estimate how filling the gap affects individuals' out-of-pocket spending and medication use, separately for branded and generic drugs. One important difficulty in estimating the policy impact is that around the same time, many blockbuster drugs commonly used by the Medicare population experienced patent expiration and began to see generic entry. Because generic entries affected different therapeutic classes at different times, we run difference-in-differences models by therapeutic category at the beneficiary-month level to isolate the effect of the gap closure from that of generic entry. Overall, we find that filling the gap substantially reduced out-of-pocket spending and increased the use of branded drugs, which had larger discount rates during the analysis period. Beneficiaries reaching the gap, at older ages, or with comorbidities experienced larger reduction in out-of-pocket spending. We show that without accounting for generic entry, the effect of filling the coverage gap on medication use is underestimated for branded drugs and overestimated for generic drugs.

The Inflation Reduction Act: How Will Medicare Negotiating Drug Prices Impact Patients with Heart Disease?

PURPOSE OF REVIEW: Cardiovascular medications improve health and prevent early death. However, high drug prices reduce the use of these medications and strain the health system. The Inflation Reduction Act (IRA) of 2022 allows Medicare to negotiate drug prices with manufacturers and reduces out-of-pocket drug costs for Medicare beneficiaries. This article explores the potential impact that the IRA will have on the treatment of cardiovascular disease. RECENT FINDINGS: Cardiovascular disease medications are likely to be selected for price negotiations under the IRA, leading to savings for patients and for Medicare. Recent work suggests that the IRA's reforms to the Medicare Part D drug benefit will meaningfully reduce out-of-pocket costs for important cardiovascular medications. The IRA is expected to impact cardiovascular disease treatments via price negotiations and through the broader access to medications afforded by improvements to Part D coverage design.

Prescription Drug Advertising and Drug Utilization: The Role of Medicare Part D.

This paper examines how direct-to-consumer advertising (DTCA) for prescription drugs influences utilization by exploiting a large and plausibly exogenous shock to DTCA driven by the introduction of Medicare Part D. Part D led to larger increases in advertising in geographic areas with higher concentrations of Medicare beneficiaries. We examine the impact of this differential increase in advertising on non-elderly individuals to isolate advertising effects from the direct effects of Part D. We find that exposure to advertising led to large increases in treatment initiation and improved medication adherence. Advertising also had sizeable positive spillover effects on non-advertised generic drugs. Our results imply significant spillovers from Medicare Part D on the under-65 population and an important role for non-price factors in influencing prescription drug utilization.

Coverage of New Drugs in Medicare Part D.

Policy Points Only a small minority of new drugs in "nonprotected" classes are widely covered by Part D plans nationwide in the year after US Food and Drug Administration (FDA) approval. Part D plans frequently apply utilization management restrictions such as prior authorizations to newly approved drugs in both protected and nonprotected classes. Drug price influences both formulary inclusion (in nonprotected classes) and coverage restrictions (in both protected and nonprotected classes), while other drug characteristics such as therapeutic benefits are not consistently associated with formulary design. Plans do not seem to favor the minority of drugs that are determined to offer added therapeutic benefit over existing alternatives. CONTEXT: Medicare Part D is an outpatient prescription drug benefit for older Americans covering more than 46 million beneficiaries. Except for mandatory coverage for essentially all drugs in six protected classes, plans have substantial flexibility in how they design their formularies: which drugs are covered, which drugs are subject to restrictions, and what factors determine formulary placement. Our objective in this paper was to document the extent to which Part D plans limit coverage of newly approved drugs. METHODS: We examined the formulary design of 4,582 Part D plans from 2014 through 2018 and measured (1) the decision to cover newly approved drugs in nonprotected classes, (2) use of utilization management tools in protected and nonprotected classes, and (3) the association between plan design and drug-level characteristics such as 30-day cost, therapeutic benefit, and the US Food and Drug Administration (FDA) expedited regulatory pathway. FINDINGS: The FDA approved 109 new drugs predominantly used in outpatient settings between 2013 and 2017. Of these, 75 fell outside of the six protected drug classes. One-fifth of drugs in nonprotected classes (15 out of 75) were covered by more than half of plans during the first year after approval. Coverage was often conditional on utilization management strategies in both protected and nonprotected classes: only seven drugs (6%) were covered without prior authorization requirements in more than half of plans. Higher 30-day drug costs were associated with more widespread coverage in nonprotected classes: drugs that cost less than $150 for a 30-day course were covered by fewer than 20% of plans while those that cost more than $30,000 per 30 days were covered by more than 50% of plans. Plans were also more likely to implement utilization management tools on high-cost drugs in both protected and nonprotected classes. A higher proportion of plans implemented utilization management strategies on covered drugs with first-in-class status than drugs that were not first in class. Other drug characteristics, including availability of added therapeutic benefit and inclusion in FDA expedited regulatory approval, were not consistently associated with plan coverage or formulary restrictions. CONCLUSIONS: Newly approved drugs are frequently subject to formulary exclusions and restrictions in Medicare Part D. Ensuring that formulary design in Part D is linked closely to the therapeutic value of newly approved drugs would improve patients' welfare.

Factors associated with time to EGFR TKI treatment in patients with non-squamous metastatic non-small-cell lung cancer.

Aim: Assess factors associated with EGFR TKI initiation among patients with metastatic non-small-cell lung cancer (mNSCLC). Patients & methods: Medicare Part D patients diagnosed with non-squamous mNSCLC and starting an EGFR TKI within 1 year of diagnosis were selected from the Surveillance, Epidemiology and End Results (SEER)-Medicare database. Associations between patient characteristics and time from diagnosis to treatment initiation (time-to-treatment [TTT]) were analyzed. Results: Among the sample (n = 890), the patients who were younger, African-American or from rural communities had significantly longer TTT. Patients who did not receive surgery, who were Asian and those with brain metastases had significantly shorter TTT. Conclusion: Patient demographics and clinical characteristics may affect timeliness of EGFR TKI treatment for mNSCLC. Future research should examine potential barriers to treatment.

This study aimed to identify factors that may affect the time to initiate treatment with a product in the EGFR TKI class of drugs for patients with metastatic non-small-cell lung cancer (mNSCLC). We used an anonymized database that combines health information on cancer patients (SEER) with insurance claims information for Medicare Part D patients. Our study included 890 patients. We found that patients who were younger, African­American or from rural communities had longer times to starting treatment. Patients who did not receive surgery, who were Asian and those with cancer that had spread to the brain had notably shorter times to starting treatment. Further research should examine potential barriers that may contribute to treatment initiation delay.

Reforming the Medicare Part D Benefit Design: Financial Implications for Beneficiaries, Private Plans, Drug Manufacturers, and the Federal Government.

CONTEXT: Reforming the Medicare Part D program-which provides prescription drug coverage to 49 million beneficiaries-has emerged as a key policy priority. METHODS: The authors evaluate prescription drug claims from a 100% sample of Medicare Part D beneficiaries to evaluate the current spending distribution across different payers for different types of beneficiaries across different benefit phases. They then model how these estimates would change under a proposal to redesign the Medicare Part D standard benefit. FINDINGS: Spending patterns differ for beneficiaries who do and do not qualify for low-income subsidies. Part D plans face limited liability for total spending under the current standard benefit design, amounting to 36% of total spending for beneficiaries who do not receive low-income subsidies and 28% of total spending for those who do. Proposed reforms would increase plan liability and significantly change the distribution of liability across plans, drug manufacturers, and the federal government. CONCLUSIONS: Though the original goal of the Part D program was to create a market of competing private plans that provide prescription drug coverage to Medicare beneficiaries, the standard benefit design that was included in the original legislation reflected significant political compromises. Reforming the standard benefit design to give plans more skin in the game could significantly affect competition in the market, with differential impact across drug classes and types of beneficiaries.

Pharmaceutical opioid marketing and physician prescribing behavior.

Physicians' relationships with the pharmaceutical industry have recently come under public scrutiny, particularly in the context of opioid drug prescribing. This study examines the effect of doctor-industry marketing interactions on subsequent prescribing patterns of opioids using linked Medicare Part D and Open Payments data for the years 2014-2017. Results indicate that both the number and the dollar-value of marketing visits increase physicians' patented opioid claims. Furthermore, direct-to-physician marketing of safer abuse-deterrent formulations of opioids is the primary driver of positive and persistent spillovers on the prescribing of less safe generic opioids - a result that we show appears to be driven by insurance coverage policies. These findings suggest that pharmaceutical marketing efforts may have unintended public health implications.

How protected classes in Medicare Part D influence U.S. drug sales, utilization, and price.

When the Medicare Part D prescription drug benefit was implemented in 2006, six drug classes were designated "protected classes." Because responsibility for obtaining favorable drug prices depends on private insurers' abilities to negotiate with pharmaceutical manufacturers using the threat of formulary exclusion, the protected class designation could undermine the insurers' ability to control spending and utilization of drugs in these six classes. I estimate the effect of the protected class policy on U.S. national drug sales, utilization, and price using 2001-2010 IMS Health National Sales Perspectives data and Verispan Vector One: National data and controlling for drug and year fixed effects. I find that protected status beginning in 2006 led to $112-121 million per drug per year higher U.S. sales for drugs in protected classes relative to unprotected drugs. Greater sales were driven by the antidepressant, antipsychotic, anticonvulsant, and antineoplastic classes. Subsequent analyses on a subset of drugs reveal that increases in both price and quantity are responsible for the growth of sales in protected class drugs. These results are important for informing the recent and ongoing deliberation by the Medicare program over whether to remove several classes from protection.

Patterns of pain medication use associated with reported pain interference in older adults with and without cancer.

CONTEXT: Concerns about the adequacy of pain management among older adults are increasing, particularly with restrictions on opioid prescribing. OBJECTIVES: To examine associations between prescription pain medication receipt and patient-reported pain interference in older adults with and without cancer. METHODS: Using the 2007-2012 Surveillance Epidemiology and End Results (SEER)-Medicare Health Outcomes Survey (MHOS) database linked to Medicare Part D prescription claims, we selected MHOS respondents (N = 15,624) aged ≥ 66 years, ≤ 5 years of a cancer diagnosis (N = 9105), or without cancer (N = 6519). We measured receipt of opioids, non-steroidal anti-inflammatory drugs, and antiepileptics, and selected antidepressants within 30 days prior to survey. Patient-reported activity limitation due to pain (pain interference) within the past 30 days was summarized as severe, moderate, or mild/none. Logistic regression using predictive margins estimated associations between pain interference, cancer history, and pain medication receipt, adjusting for socio-demographics, chronic conditions, and Part D low-income subsidy. RESULTS: Severe or moderate pain interference was reported by 21.3% and 46.1%, respectively. Pain medication was received by 21.5%, with 11.6% receiving opioids. Among adults reporting severe pain interference, opioid prescriptions were filled by 27.0% versus 23.8% (p = 0.040) with and without cancer, respectively. Over half (56%) of adults reporting severe pain in both groups failed to receive any prescription pain medication. CONCLUSIONS: Older adults with cancer were more likely to receive prescription pain medications compared with adults without cancer; however, many older adults reporting severe pain interference did not receive medications. Improved assessment and management of pain among older adults with and without cancer is urgently needed.

The concomitant use of tyrosine kinase inhibitors and proton pump inhibitors: Prevalence, predictors, and impact on survival and discontinuation of therapy in older adults with cancer.

BACKGROUND: The concomitant use of tyrosine kinase inhibitors (TKIs) and proton pump inhibitors (PPIs) is a significant concern because of potential drug-drug interaction that reduces TKI absorption, thus potentially reducing the effectiveness of TKIs. The objective of this study was to evaluate the prevalence and predictors of concomitant TKI-PPI receipt and its impact on survival and therapy discontinuation in older adults with cancer. METHODS: This retrospective study used linked Surveillance, Epidemiology, and End Results-Medicare data for the years 2007 through 2012. In total, 12,538 patients with lung cancer, renal cell cancer, chronic myelogenous leukemia, liver cancer, or pancreatic cancer were included. The primary exposure variable was concomitant receipt of TKI-PPI, defined as at least 30 days of PPI use in the first 90 days from the start of the TKI (exposure period). The outcomes measured were overall survival and discontinuation of therapy in 90 days and 1 year after the end of the exposure period. Cox proportional-hazards regression with inverse probability of treatment weighting was used to evaluate the association between exposure and outcome. RESULTS: The overall prevalence of TKI-PPI receipt was 22.7%. Predictors that were associated with increased use included polypharmacy and prior PPI receipt. TKI-PPI use decreased survival in 90 days (hazard ratio, 1.16; 95% confidence interval, 1.05-1.28) and in 1 year (hazard ratio, 1.10; 95% confidence interval, 1.04-1.18) but was not associated with discontinuation. CONCLUSIONS: Nearly 1 in 4 older adults with cancer who receive TKIs also receive PPIs concomitantly, and concomitant use is associated with an increased risk of death. Concerted efforts to manage medications are needed to identify and reduce the receipt of PPIs when TKIs are initiated.

Low Utilization of Beta-Blockers Among Medicare Beneficiaries Hospitalized for Heart Failure With Reduced Ejection Fraction.

BACKGROUND: The evidence-based beta-blockers carvedilol, bisoprolol, and metoprolol succinate reduce mortality and hospitalizations among patients with heart failure with reduced ejection fraction (HFrEF). Use of these medications is not well described in the general population of patients with HFrEF, especially among patients with potential contraindications. OBJECTIVES: Our goal was to describe the patterns of prescription fills for carvedilol, bisoprolol, and metoprolol succinate among Medicare beneficiaries hospitalized for HFrEF, as well as to estimate the associations between specific contraindications for beta-blocker therapy and those patterns. METHODS AND RESULTS: With the use of the cohort of 15,205 Medicare beneficiaries hospitalized for HFrEF from 2007 to 2013 in the 5% Medicare random sample, we described prescription fills (30 days after discharge) and dosage patterns (1 year after discharge) for beta-blockers. By means of of Fine and Gray competing risk models, we estimated the associations between potential contraindications (hypotension, chronic obstructive pulmonary disease [COPD], asthma, and syncope) and prescription fill and dosing patterns while adjusting for demographics, comorbidities, and health care utilization. For beneficiaries who did not die or readmitted to the hospital, 38% of hospitalizations were followed by a prescription fill for an evidence-based beta-blocker within 30 days, 12% were followed by prescription fills for at least 50% of the recommended dose of an evidence-based beta-blocker within 1 year, and 9% were followed by a prescription fill for an up-titrated dose of an evidence-based beta-blocker within 1 year. The prevalence of the contraindications were 21% for hypotension, 48% for COPD, 15% for asthma, and 12% for syncope. Among beneficiaries who did not fill a prescription for an evidence-based beta-blocker within 30 days, 67% had at least 1 of these contraindications. Hypotension, COPD, and syncope were each associated with a ∼10% lower risk of filling a prescription for an evidence-based beta-blocker. CONCLUSIONS: Prescription fill and up-titration rates for evidence-based beta-blockers are low among Medicare beneficiaries with HFrEF, but contraindications explain only a minor part of these low rates.

Older Medicare Beneficiaries Frequently Continue Medications with Limited Benefit Following Hospice Admission.

BACKGROUND: The use of medications not relieving symptoms or maximizing quality of life should be minimized following hospice enrollment. OBJECTIVE: To evaluate the frequency of and predictive factors for continuation of medications with limited benefit after hospice admission among those admitted for cancer- and non-cancer-related causes. DESIGN: Cohort study using the Surveillance, Epidemiology and End Results-Medicare linked database. PATIENTS: Medicare Part D-enrolled beneficiaries 66 years and older who were admitted to and died under hospice care between January 1, 2008, and December 31, 2013 (N = 70,035). MAIN MEASURES: Patients were followed from hospice enrollment through death for Part D dispensing of limited benefit medications (LBMs) they had used in the 6 months prior to hospice admission, including anti-hyperlipidemics, anti-hypertensives, oral anti-diabetics, anti-platelets, anti-dementia medications, anti-osteoporotic medications, and proton pump inhibitors. The proportion of patients continuing an LBM after hospice admission was evaluated. Adjusted relative risks (RRs) were estimated for factors associated with LBM continuation. KEY RESULTS: Overall, 29.8% and 30.5% of patients admitted to hospice for a cancer- and non-cancer-related cause, respectively, continued at least one LBM after hospice admission. Anti-dementia medications were continued most frequently (29.3%) while anti-osteoporotic medications were continued least often (14.1%). Compared to home hospice, LBM continuation was greater in hospice patients residing in skilled nursing (RR 1.25, 95% CI 1.20-1.29), non-skilled nursing (RR 1.29, 95% CI 1.25-1.32), and assisted living facilities (RR 1.28, 95% CI 1.24-1.32). Patients with hospice stays ≥ 180 days were more likely to continue at least one LBM compared to those with stays of 1 week or less (RR 13.11, 95% CI 12.25-14.02). CONCLUSIONS: A substantial proportion of Medicare hospice beneficiaries continued to receive LBMs following hospice enrollment. Providers should evaluate the necessity of continuing non-palliative medications at the end of life through a careful, patient-centric consideration of their potential risks and benefits.

Impact of Medicare Part D on mental health treatment and outcomes for dual eligible beneficiaries with HIV.

Depression is common among women with HIV and untreated depression can result in poor quality of life and worsen HIV outcomes. Women with HIV who are dually enrolled in Medicaid and Medicare faced a potential disruption in medication access when Medicare Part D was implemented in 2006. The goal of this study was to estimate the effects of Medicare Part D implementation on antidepressant use, depressive symptoms, and hospitalization in Medicaid-Medicare dual eligible women with HIV. This study used 2003-2008 data from the Women's Interagency HIV Study. The effects of Medicare Part D were estimated using a difference-in-differences approach, adjusting for temporal trends using a matched control group of Medicaid-only enrollees. Before Medicare Part D implementation, dual eligibles differed from Medicaid-only enrollees in antidepressant use and hospitalization, despite having identical prescription drug coverage through Medicaid. For dual enrollees, the transition to Medicare Part D was not associated with changes in antidepressant use, depressive symptoms, or hospitalization. We did not find disruptive effects on antidepressant use and related outcomes among dual eligibles in this study. Stable antidepressant use may be due to better access to medical care for dual eligibles through Medicare both before and after Medicare Part D implementation, which may have eclipsed any effects of the transition. It may also signal that classification of antidepressants as a protected drug class under Medicare Part D was effective in preventing psychiatric medication disruption.

The impact of Medicare part D on income-related inequality in pharmaceutical expenditure.

BACKGROUND: Income-related inequality measures such as the concentration index are often used to describe the unequal distribution of health, health care access, or expenditure in a single measure. This study demonstrates the use of such measures to evaluate the distributional impact of changes in health insurance coverage. We use the example of Medicare Part D in the United States, which increased access to prescription medications for Medicare beneficiaries from 2006. METHODS: Using pooled cross-sectional samples from the Medical Expenditure Panel Survey for 1997-2011, we estimated income-related inequality in drug expenditures over time using the concentration and generalised concentration indices. A difference-in-differences analysis investigated the change in inequality in drug expenditures, as measured using the concentration index and generalised concentration index, between the elderly (over 65 years) and near-elderly (54-63 years) pre- and post-implementation of Medicare Part D. RESULTS: Medicare Part D increased public drug expenditure while out-of-pocket and private spending fell. Public drug expenditures favoured the poor during all study periods, but the degree of pro-poorness declined in the years immediately following the implementation of Part D, with the poor gaining less than the rich in both relative and absolute terms. Part D also appeared to result in a fall in the pro-richness of private insurance drug expenditure in absolute terms but have minimal distributional impact on out-of-pocket expenditure. These effects appeared to be short lived, with a return to the prevailing trends in both concentration and generalised concentration indices several years following the start of Part D. CONCLUSIONS: The implementation of Medicare Part D significantly reduced the degree of pro-poorness in public drug expenditure. The poor gained less of the increased public drug expenditure than the rich in both relative and absolute terms. This study demonstrates how income-related inequality measures can be used to estimate the impact of health system changes on inequalities in health expenditure and provides a guide for future evaluations.

The effect of prescription drug insurance on health behavior: Evidence from Medicare Part D.

This paper provides empirical evidence on the health behavior effect of prescription drug insurance. Using the difference in the regression discontinuity research design, I compare health behavior changes at age 65 before and after the introduction of Medicare Part D. I find that the implementation of Medicare Part D increased prescription drug insurance coverage and reduced out-of-pocket spending per prescription and the use of cardiovascular and metabolic therapeutic class drugs. I also find that Medicare Part D led to a 6.36 percentage point decrease in the probability of engaging in moderate physical exercise and a 27.4 percentage point decrease in the amount of time spent on moderate physical activity. It also increased the probability of being overweight by 5.75 percentage points. Its effects on vigorous and muscle-strengthening exercise both at the extensive and intensive margins, obesity, BMI, and cigarette consumption are not statistically significant.

Adherence to tyrosine kinase inhibitors among Medicare Part D beneficiaries with chronic myeloid leukemia.

BACKGROUND: Tyrosine kinase inhibitors (TKIs) improve the survival of patients with chronic myeloid leukemia (CML) dramatically; however, nonadherence to TKI therapy may lead to resistance to the therapy. TKIs are very expensive and are covered under Part D insurance for Medicare patients. To the authors' knowledge, the impact of low-income subsidy status and cost sharing on adherence among this group has not been well studied in the literature. METHODS: Surveillance, Epidemiology, and End Results (SEER) registry data linked with Medicare Part D data from the years 2007 through 2012 were used in the current study. The authors identified 836 patients with CML with Medicare Part D insurance coverage who were new TKI users. Treatment nonadherence was defined as a binary variable indicating the percentage of days covered was <80% during the 180-day period after the initiation of TKI therapy. Logistic regression was used to examine the relationship between out-of-pocket costs per 30-day drug supply, Medicare Part D plan characteristics, and treatment adherence while controlling for other patient characteristics. RESULTS: Overall, 244 of the 836 patients with CML (29%) were nonadherent to targeted oral therapy during the 180 days after the initiation of treatment with TKIs. The multivariable logistic regression demonstrated that patients with heavily subsidized (odds ratio, 6.7; 95% confidence interval, 2.8-15.9) and moderately subsidized (odds ratio, 3.0; 95% confidence interval, 1.4-6.5) Medicare Part D plans were much more likely to demonstrate nonadherence compared with patients without a subsidy. CONCLUSIONS: The current population-based study found a significantly higher rate of nonadherence among heavily subsidized patients with substantially lower out-of-pocket costs, which suggests that future research is needed to help lower the nonadherence rate among these individuals. Cancer 2018;124:364-73. © 2017 American Cancer Society.