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Letter to the Editor |
a John Radcliffe Hospital, Headington, Oxford, United Kingdom; b Johnson and Johnson Pharmaceutical Services, LLC, Raritan, New Jersey, USA; c Liberty Mutual Group, Boston, Massachusetts, USA (formerly of Policy Analysis Inc., Brookline, Massachusetts, USA)
Correspondence: Timothy J. Littlewood, M.D., John Radcliffe Hospital, Headington, OX3 9DU, Oxford, United Kingdom. Telephone: 44-0-1865220331; Fax: 44-0-1865221778; e-mail: tim.littlewood{at}bitinternet.com
Received August 25, 2005; accepted for publication September 15, 2005.
We appreciate the letter from Dr. Coiffier in response to our recently published article, "Effect of Patient Exclusion Criteria on the Efficacy of Erythropoiesis-Stimulating Agents in Patients with Cancer-Related Anemia" [1]. As stated in the discussion section of our manuscript, we firmly agree with Dr. Coiffier that the hematologic outcomes of erythropoiesis-stimulating agents (ESAs) can be influenced by such factors as patient disease stage, type and intensity of previous and current treatment, and comorbidities [2]. Indeed, this is the focus and primary conclusion of our study, namely that a trial’s inclusion/ exclusion criteria may have a rather profound effect on observed results and, therefore, that these factors should be carefully considered when one attempts to compare results between any two clinical trials.
For this reason, we are quite surprised by one of the main suggestions put forth by Dr. Coiffier that clinically relevant differences exist between epoetin alfa and epoetin beta. He suggests that there are differences between these two ESAs with regard to their isoform composition, bioactivity, absorption, and reticulocyte response that support different dosing requirements between the agents. This seems slightly peculiar, first because epoetin alfa and epoetin beta share an identical amino acid sequence perfectly analogous to the endogenous erythropoietin hormone, and second because no clinical trials to date have suggested there exist clinical differences between the two ESAs.
As the title of our article describes, the purpose of our study is to demonstrate the impact that certain patient inclusion/exclusion criteria can have on the results observed in clinical trials. In no way is it intended as a clinical comparison of epoetin alfa and epoetin beta.
Instead, we evaluated the effect of the strict criteria (e.g., baseline Hb between 9 g/dl and 11 g/dl with no transfusion history within 2 months prior to baseline and serum erythropoietin level 
100 mU/ml) used in the NeoRecormon® (F. Hoffman-La Roche Ltd., Basel, Switzerland, http://www.roche.com) Once Weekly (NOW) trial on the outcomes observed in a previously conducted trial with epoetin alfa [3]. Our results demonstrated that only 27% of patients with hematologic malignancies in the epoetin alfa trial would have been eligible for inclusion in the epoetin beta trial and that outcomes were markedly better in epoetin alfa–treated patients who met these criteria than in those who did not.
These results continue to suggest that the criteria used in the NOW trial cannot be generalized to patients seen in standard clinical practice and likely select for a patient population more likely to respond to ESA therapy.
We firmly agree with Dr. Coiffier that the "comparison of different clinical trials of ESAs does not allow evaluation of the relative efficacy of each ESA" [1]. For this reason, we feel his suggestion that clinically relevant differences exist between the two ESAs is neither supported by the available evidence nor promoted by our study. The primary conclusion from our study therefore appears to remain undisputed: that certain inclusion/exclusion criteria from a clinical trial can have a profound effect on the results observed and that these criteria should be carefully considered by the medical community when attempts are made to use these results to inform on clinical practice decisions.
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  B. Coiffier Response to "Effect of Patient Exclusion Criteria on the Efficacy of Erythropoiesis-Stimulating Agents in Patients with Cancer-Related Anemia" Oncologist, October 1, 2005; 10(9): 762 - 763. [Full Text] [PDF]
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