A new observational study of the tumor necrosis factor-alpha (TNF-α) inhibitors infliximab and etanercept has found that Medicare patients with RA are 30% more likely to receive the intravenous drug infliximab than those covered by private insurance, findings that suggest that reimbursement policies may drive physicians' prescribing decisions independently of efficacy.

However, the authors of the study, which appears in the January 9 issue of the Archives of Internal Medicine,¹ report that the advent of Medicare Part D prescription coverage may change physicians' prescribing behavior to favor self-injectable drugs.

"The clinician may [base] medical decisions on the prescription coverage that the Medicare patient happens to have chosen, rather than on clinical judgment alone," lead study author Esi Morgan DeWitt, MD, a pediatric rheumatologist at Duke University Medical Center in Durham, North Carolina, tells CIAOMed.

"Given that clinical trials tout roughly comparable efficacy between the drugs, the preferential prescribing of one TNF-α inhibitor over the others may not [have made] a big [difference] in terms of disease outcome. However, it did not account for patient preferences, as many patients did not have a choice of drug," Dr. DeWitt says. "Furthermore, from clinical experience, it is evident that some patients respond to TNF-α inhibitors differently, [and] one drug does not suit all patients."

The findings emerged from an observational cohort study of 1663 patients with RA who were newly prescribed etanercept or infliximab after enrollment in the National Databank for Rheumatic Diseases. Dr. Dewitt and colleagues performed univariate and multivariable analyses of patient demographic and disease characteristics to identify independent predictors of the prescribing of the biologic drug. Notably, the researchers found that patients treated with etanercept were less likely than those receiving infliximab to have public insurance, 29% and 60.3%, respectively (P <.001).

In multivariable analyses, type of insurance plan, age, educational level, Short Form 36 physical component scores, and treatment with methotrexate were significant independent predictors of the choice of biologic agent, whereas disease characteristics generally were not strong predictors. "The variables that most favored prescription of infliximab over etanercept were treatment with methotrexate, age (> 65 years), and public insurance plan," the investigators say.

Medicare Part D may change prescribing behavior

Now that Medicare Part D is in effect, more Medicare patients will have access to self-injectable intramuscular TNF-α agents, including subcutaneous etanercept and adalimumab, in addition to access to infusion drugs (infliximab) if enrolled in Medicare Part B.

Exactly how the advent of Medicare Part D will affect physician prescribing behavior remains to be seen, Dr. DeWitt says. "Going forward, it is not clear if patients above a certain income cutoff will be able to afford the large co-payments associated with self-administered drugs, which require catastrophic coverage levels and subject patients to payment within the ‘doughnut hole'," he says. Medicare's basic Part D benefit pays 75% of the cost of prescriptions, up to $2,250 per year. Benefits then stop until your costs reach $3,600, after which Medicare pays 95% of the patient's costs. This gap is Part D's "doughnut hole." The current study found that the income of patients treated with etanercept was $10,800 higher than those in the infliximab group (P <.001).

"Medicare is certainly going to face a ballooning in costs ... if coverage continues under Part D," Dr. DeWitt says. "One can only imagine that the premiums facing the patient will continue to grow to reflect the higher drug costs, given the trend of more cost shifting to the consumer.

"Whether the patient co-payment under Part B will be relatively less, continuing to favor choice of infusion drugs, remains to be seen," he says. "One would anticipate a relative shift towards self-injection drugs compared to prior emphasis on infusion drugs due to the feasibility of reimbursement. In either event, the physician is going to be forced to become more involved in and aware of patients' insurance coverage, which may increasingly influence medical prescribing."

In an editorial accompanying the new study,² Wendy Levinson, MD, and Andreas Laupacis, MD, of the University of Toronto in Ontario, Canada, agree. They write that in the future, physicians and patients must have an open discussion about out-of-pocket costs.

"We believe that physicians should acquire the skills to discuss potentially sensitive financial issues with patients so they can make treatment choices with complete information," they write. "Physicians will need to consider individual formularies of an individual patient's health care plan."

References

1. DeWitt EM, Glick HA, Albert AD, et al. Medicare coverage of tumor necrosis factor-α inhibitors as an influence on physicians' prescribing behavior. Arch Intern Med. 2006;166:57-63.
2. Levinson W, Laupacis A. Call for fairness in formulary decisions. Arch Intern Med. 2006;166:16-18.