In the 1950’s and 1960’s word began to spread about laetrile, and although it was not approved for treatment by the FDA, doctors like John A. Richardson M.D. began using it at his clinic in San Francisco. His results with laetrile is documented in the book Laetrile Case Histories: The Richardson Cancer Clinic Experience by John A. Richardson M.D. and Patricia Irving, R.N. Originally written in 1977, the book was updated in 2005 with follow ups on the patients they treated.