Laetrile

From Research Methods in Psychology (p. 317):

...[D]uring the early 1980s considerable controversy surrounded the supposed cancer-curing drug laetrile. Few respectable scientists or medical researchers considered this drug to be beneficial in the treatment of cancer. Advocates of laetrile, however, presented case studies reporting positive results. Largely because of public pressure, the government carried out systematic and expensive tests of the drug under controlled conditions. Researchers did not find beneficial effects of the drug in controlled experiments. As critics of laetrile have commented, many patients who used laetrile instead of traditional therapies may have postponed or interrupted valid courses of treatment and thus contributed to the spread of their cancer.