The Food and Drug Administration’s 2007 “boxed warning” about serious adverse events associated with the use of erythropoietin-stimulating agents (ESAs) was followed by a substantial reduction in their use among patients recovering from colorectal, breast, or lung cancer, according to a new report.

Boxed warnings are considered one of the strongest mechanisms with which the FDA can communicate concerns about drug safety to the public. However, some critics have questioned the effectiveness of these warnings, and the available evidence “remains inconclusive, largely because almost all of [the data] were drawn from observational studies using pre-post designs without control groups,” said John Bian, PhD , of the University of South Carolina College of Pharmacy and Hollings Cancer Center, Columbia, and his associates.

They assessed the effectiveness of boxed warnings concerning ESAs such as epoetin and darbepoetin that are used to treat chemotherapy-induced anemia. These biologics have been tied to serious adverse events including venous thromboembolism and death in certain patients. The warning specifically targeted their use in colorectal, breast, and lung cancer.

The investigators analyzed data in the SEER cancer registry for the period immediately before and immediately after the 2007 boxed warning was issued. Their sample comprised 45,319 patients aged 66 years and older who were treated either in the “pre” warning period (January 2004-September 2006) or the “post” period (April 2007-September 2009). This included a control group of 3,375 patients with myelodysplastic syndromes. Use of ESAs in these patients was off-label and was not targeted by the boxed warning (J Clin Oncol. 2017 Apr 25. doi: 10.1200/JCO.2017.72.6273 ).

The use of ESAs declined sharply after the boxed warning was issued, except in the control group. The proportion of breast cancer patients receiving ESAs dropped from 49%-55% before 2007 to 30% in 2007, 16% in 2008, and 9% in 2009.

Similarly, the proportion of colorectal cancer patients receiving ESAs declined from about 35%-40% before 2007 to 18% in 2007, 11% in 2008, and 9% in 2009. The proportion of lung cancer patients receiving ESAs decreased from 56%-58% before 2007 to 40% in 2007, 29% in 2008, and 24% in 2009. In contrast, the proportion of patients with myelodysplastic syndromes receiving ESAs – the control group – remained relatively stable at 39%-42% before 2007, 35% in 2007, and 32% in 2008 and 2009.

This represents a reduction of approximately 40% overall in the use of ESAs among targeted patients after the warning was issued. However, this decrease appeared to have little effect on the incidence of hospitalization for venous thromboembolism in this patient population, Dr. Bian and his associates noted.

The study was supported by the National Institutes of Health. Dr. Bian reported having no relevant financial disclosures. His associates reported ties to Quincy Bioscience, Bristol-Myers Squibb, Taiho Pharmaceutical, Mylan, Eli Lilly, Merck, Amgen, and BDI Pharma.