As of 2015, there are no clinical trials testing the efficacy of Rick Simpson's hemp oil as a cancer treatment. However, Cancer Research UK reports that there is one clinical trial of cannabis as a cancer treatment, which has published results.
Cancer Research UK reports that a 2006 clinical trial of the beneficial effects of cannabis on late-stage cancer showed that eight out of nine patients responded to the treatment. However, all patients succumbed within a year to their illness. Cancer Research UK notes that since the 1970s, scientists have published hundreds of scientific papers that discuss the potential anticancer properties of cannabinoids. However, the organization concludes that there are many unanswered questions and preclinical research does not provide any proof of cannabinoids' ability to treat cancer.