Results
Of the 500 mailed surveys, 33 (6.6%) were nondeliverable because of incorrect addresses. A total of 56 (12%) of the remaining 467 surveys were returned. Two of the returned surveys were incomplete due to formulary issues, and one was inadvertently sent to a radiation oncology office. These surveys were not included in the analysis of the survey questions because the participants did not fill out the returned survey. The first question was "How do you calculate adult carboplatin doses at your practice?" A majority of participants (92.6% [n = 54]) responded with the AUC method. Three participants (5.5% [n = 54]) did not answer the first question. Only one participant responded with BSA method (1.9%), and if this answer was chosen, then the survey was to be returned without answering questions 2 through 7. Questions 2 through 6 were multiple-choice answers, and participants could circle all methods that applied and had the option of choosing "other" if the desired method was not stated.
When asked who calculates carboplatin AUC doses, multiple health professionals (40% [n = 53]) were selected most commonly. A registered nurse was the most common single response (26% [n = 53]). Respondents who indicated "other" noted an electronic medical record, medical doctor, oncology physician assistant, or computer-calculated carboplatin AUC doses. When asked about double check or verification, the most common selection was multiple clinicians (51%) and the most common single selection was a registered nurse (26%). One respondent indicated that he/she did not double check or verify. When asked about what to do if a patient had a SCr of 0.4 mg/dL, the majority answered that they would use the 0.4 mg/dL in their dose calculation (25%). The second most common response was to use 0.8 mg/dL (15% [n = 53]). Those who answered "other" stated that it was physician dependent, that the CrCl was capped, or that the SCr was rounded to 0.5, 0.7, or 0.9 mg/dL. When asked about the patient weight used in carboplatin calculations, the majority answered actual body weight (57% [n = 53]). Those who answered "other" stated that a different ideal body weight formula was used than that provided in the survey. When asked about which formula was used, the most common response was CG (38% [n = 53]). The second most common response was entering patient data into an automated carboplatin AUC dose calculator on a computer, personal digital assistant, website, slide rule, or standard form. Participant-provided responses for "other" included "slide rule," "each oncologist uses their own," or "Chatelut formula." The Chatelut formula was designed as an alternative to the CF but is not nearly as widely used as the CF or the MCFs and is not discussed in this article.
The patient case example provided in online Appendix 1 pertained to the final question of the survey. The case example was reviewed to assess if the carboplatin AUC 6 doses were different at different practices for a single patient with the same patient variables. A total of 47 of 53 (88%) participants answered the case example question. Participants' responses indicated a carboplatin dose range of 110 to 1,811 mg (mean 978 mg, median 948 mg). We determined a correct dose of 721 mg for the case example question, and only 1 participant (of 47) indicated the same response.
In addition, when assessing the case example question, several responses contained errors (15% [n = 53]). Among those responses, 63% (n = 8) involved calculation errors from using the wrong order of operations, such that the formula was accurately written but the calculation method was incorrect. More than one-third (37%) of the errors resulted from omitting certain variables, such as the female factor in the Jelliffe equation, AUC, or the nonrenal elimination constant 25 in the MCF equation.