A major reason is probably nuclear pollution. Nuclear tests have been replaced by radioactive waste and the results of many small and large incidents in nuclear

A major reason is probably nuclear pollution. Nuclear tests have been replaced by radioactive waste and the results of many small and large incidents in nuclear facilities. An accident like Fukushima pollutes the whole planet, not just Japan and some parts of the Pacific. It would be much easier to fight such major reasons for cancer instead of trying to cure cancer.