Methodology Flaws and Implications of a Complementary Medicine Study

To the Editor In a retrospective case-control study using records from the US National Cancer Database with 1:4 matching of 258 vs 1032 patients with cancer, Johnson et al¹ reported: (1) reduced survival among the 258 patients who used at least 1 conventional treatment together with complementary medicine (CM) compared with the 1032 patients who used only conventional treatment and (2) an association between the use of CM and refusal of standard treatment. The authors concluded that such refusal may explain the reduced survival. Herein, we briefly argue why we are not convinced that the authors’ results support their conclusion.