Cancer-related complementary and alternative medicine online: factors affecting information retrieval.

Cancer patients increasingly turn to the Internet for health information. As the use of complementary and alternative medicine (CAM) is also increasing, we studied the likelihood that consumers will incidentally encounter CAM information while searching the Internet and the factors that influence CAM information retrieval. We evaluated results retrieved from ten cancer-related searches in six common search engines, and found that 16.2% of 1121 results contained CAM information. Sponsored (i.e. paid) results contained more CAM information than non-sponsored results (38% vs. 7.5%, p<0.001). Sponsored results in the Overture and Google search engines accounted for 51% and 39% of results on the first page. These search engines also retrieved the most CAM web pages. The type of cancer used as the search keyword did not influence the number of CAM-related web pages retrieved. However, the synonyms of cancer used as search keywords differed in their retrieval of CAM web pages (p<0.001). We conclude that clinicians should help consumers recognize sponsored listings and encourage search engines to clearly identify sponsored results.