To the Editor The recently published study by Johnson et al1 evaluating the effect of complementary medicine (CM) use on survival in patients receiving curative cancer treatment is being misrepresented as evidence that CM may be harmful. There are 2 major methodological issues that challenge the validity of this study.
First, the classification of those who used CM and those who did not is likely inaccurate. As the authors point out and as is supported by epidemiologic studies, “between 48% and 88% of patients with cancer have reported the use of CAM [complementary and alternative medicine] as part of their therapy.”1(p1376) As a result of their classification, however, only 0.01% of 1 901 815 patients were classified as using CM. In order to be coded a CM user, the treating oncologist had to check a box titled “Other-Unproven: Cancer treatments administered by nonmedical personnel.” It is likely that only the most extreme examples of treatment refusal or use of unrecommended approaches were included in the 258 people who were classified as CM users. Clearly, this is an underrepresentation of the target population, as at least half should have been classified as CM users. This also means that likely half or more of those classified as “nonusers” were in fact using CM, rendering the study results invalid.