The Yale researchers identified CMs users by looking back through the clinical records of a group of patients on the US National Cancer Database and identifying those where Complementary Medicine was mentioned in their clinical records (in other words they did not ask the patients about their use of CM, but only looked at historic hospital records).
Of the 1,901,815 records they examined they found only 258 where CM was documented in the clinical records. This gives an estimated prevalence of CM use of 0.01% in the cancer population, whereas several published patient surveys have documented CM use as between 49% and 83% of the cancer population (depending on how CM is defined), with most using CM to increase quality of life and wellbeing3,4,5,6, and reduce side effects of treatment. Less than half of those using CM informed their clinicians about their CM use7. This enormous difference in CM use prevalence estimation is likely to reflect a significant problem with the Yale researchers’ methods and the applicability of their findings to a wider CM-using population.
Indeed, the authors themselves mention this in their discussion of the study limitations: “[Our analysis is limited by its retrospective and observational nature. The use of CM was likely under-ascertained given patients’ hesitancy to report its use to clinicians and for database registrars to code this use reliably.] [In addition, it is possible that clinicians were more likely to document the use of CM when patients were using noteworthy therapies that may have resulted in refusal of CCT]2”. In other words, the group of patients identified by the Yale researchers were likely to be a small, atypical group of people using some highly controversial and questionable CM modalities, which resulted in their clinicians being sufficiently concerned to document this in the clinical records, and which probably also led to them being more likely to turn down conventional treatment and pursue a more “alternative” treatment path.