Caspofungin Versus Liposomal Amphotericin B

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To the Editors: The study published in the May 2010 issue of the journal by Maertens et al1 addresses an interesting issue in a particular population usually not included in clinical trials. The study compares caspofungin and liposomal amphotericin B for the empiric antifungal therapy on pediatric prolonged febrile neutropenia patients. We would like to point out one important issue. This study is similar to a very relevant noninferiority trial, published in 2004 by some of the same authors2 taking part in this trial. At that time, the adult population was studied with a much larger sample, having more than 1000 patients randomized. The current study included a much smaller sample; however, a sample size calculation was not described and, therefore, the power of the study is unknown. The authors clearly mention that their intention was to estimate safety and tolerability, having efficacy as a secondary outcome. Notwithstanding, it concludes that many primary and secondary outcomes are in fact similar between the 2 studied groups. In our view, as the study was not designed to test noninferiority, the authors cannot conclude unequivocally that the drugs are comparable, since a difference may have not been detected because of insufficient power (beta error).3 In other words, we believe the conclusion stated by the authors that “Caspofungin and l-AmB were comparable in tolerability, safety, and efficacy as empiric antifungal therapy for persistently febrile neutropenic pediatric patients,” is too emphatic and cannot be taken solely from the results of this study and, therefore, must be confirmed in other trials before adopted in routine clinical practice. Leo Sekine, MD Epidemiology Post-Graduation Program Universidade Federal do Rio Grande do Sul [email protected] João Humbwavali Graduation on Nursing School Epidemiology Post-Graduation Program Universidade Federal do Rio Grande do Sul Fernando Herz Wolff, PhD Nêmora Tregnago Barcellos, PhD Epidemiology Post-Graduation Program Universidade Federal do Rio Grande do Sul Porto Alegre, RS, Brazil