Study: Biosimilar Filgrastim Can Improve Patient Access to FN Prophylaxis

Filgrastim, used to prevent febrile neutropenia (FN) in patients undergoing chemotherapy, is the first drug in the United States to have a biosimilar approved. Since its 2015 approval, few studies have compared the real-world incidence of FN, healthcare resource utilization, and costs among US patients using the reference product (Neupogen) and among those using the approved biosimilar (Zarxio).

A new study, published in the Journal of Managed Care & Specialty Pharmacy, reports on a retrospective claims analysis of patients with nonmyeloid cancer who were enrolled in commercial or Medicare Advantage plans between 2015 and 2016, and who received either the reference or the biosimilar filgrastim during their first observed chemotherapy cycle.

The research team, led by Lee Schwartzberg, MD, used the Optum Research Database to identify patients 18 years or older who had at least 1 claim for filgrastim following the first cycle of chemotherapy. A total of 3542 patients met inclusion criteria, of whom 172 received the biosimilar and 3370 received the reference filgrastim. Weighted cohorts were created using inverse probability of treatment weighting to arrive at a 162-patient biosimilar cohort and a 3297-patient reference cohort.

The researchers found that the incidence of FN between the weighted treatment cohorts was statistically equivalent (90% CI of the difference of percentages was within ±6%), as well as the following:

• The incidence of FN in the biosimilar cohort was 1.4% (2/162), compared with 0.9% (30/3297) in the reference cohort.
• The incidence of neutropenia with infection was 2.3% (4/162) in the biosimilar cohort versus 1.7% (57/3297) in the reference cohort.
• The incidence of neutropenia with both infection and fever was 0.0% (0/162) for the biosimilar cohort and 0.3% (10/3297) in the reference cohort.

With respect to costs, the researchers found the following:

• Among patients in both cohorts who developed FN, the proportion of who had FN-related emergency department visits ranged from 30.0% (18/60) for neutropenia with infection to 62.5% (20/32) for neutropenia with fever.
• The proportion of patients with FN-related inpatient stays ranged from 35.0% (21/60) for neutropenia with infection to 70% (7/10) for neutropenia with both infection and fever.
• Mean FN-related medical costs were $11,977 (SD, $18,383) for neutropenia with fever; $8040 (SD, $14,809) for neutropenia with infection; and $21,733 (SD, $30,003) for neutropenia with both infection and fever.
• Hospital costs represented the largest proportion of total medical costs for all cases of neutropenia involving inpatient care.

Considering the high cost of FN and the potential for prophylaxis with filgrastim to save on costs, say the authors, underutilization of the reference and biosimilar filgrastim has serious consequences in terms of healthcare costs.

“Given that [the biosimilar] is less costly than [the reference]…increasing use of the biosimilar has the potential to promote guideline compliance by improving drug access,” write the authors. “This scenario has already been borne out in Europe, where burgeoning acceptance of biosimilar filgrastim since its 2008 approval has led to more widespread use of prophylaxis, suggesting that health care providers are more able and/or willing to follow clinical guidelines now that the biosimilar is available.”

Reference

Schartzberg LS, Lal LS, Balu S, et al. Clinical outcomes of treatment with filgrastim versus a filgrastim biosimilar and febrile neutropenia—associated costs among patients with nonmyeloid cancer undergoing chemotherapy [published online April 24, 2018]. J Manag Care Spec Pharm. doi: 10.18553/jmcp.2018.17447.