Cancer claims exposed

Research into claims of animal tests helping discover cancer drugs have been investigated.

In reply to a recent enquiry from an Animal Aid supporter, Cancer Research UK (CRUK) offered three examples of ‘how the use of animals in our research has resulted in life saving scientific progress’, and implied that they were ‘effective anti-cancer treatments’ (see email from CRUK). These examples were: the breast cancer drug tamoxifen; drugs that affect the blood supply to tumours (including the novel drug Combretastatin); and work on the p53 gene pathway. We must presume that these examples embodied the best defence CRUK could offer of its pro-animal research strategy.

Animal Aid’s Victims of Charity report had already concluded that claims made for the efficacy of a multitude of cancer therapies, based on animal research, are often dashed when these are tested in people. Anti-cancer drugs in particular have a spectacular failure rate of around 95 per cent in Phase III clinical trials. We were also aware that drugs designed to cut off the blood supply to tumours have not been a clinical success, and that the development of tamoxifen was complicated by misleading data from animal experiments.

Animal Aid therefore undertook to research these three CRUK examples. We verified that, in two cases, any claim of life-saving or effective treatments was highly dubious. Combretastain and many similar drugs have failed to show survival benefits in several clinical trials. The discovery of the p53 gene pathway occurred in 1979. It has to date led to just one drug being licensed in China, the effectiveness of which is highly contested. It seems that only tamoxifen has a solid evidence base as a life-saving discovery. However, long-term toxicological studies on rats produced a high percentage of large and fast-growing liver tumours. Had these revealing rat tests been completed before the drug was marketed, there would have been powerful calls to prevent its use in cancer patients.