The present invention is based on the finding that the inhibition of the proliferation of cancer cells by cannabinoids is brought about more effectively by combined treatment with low dose naltrexone (LDN) or 6-ß-naltrexone (6BN), a metabolite of naltrexone. There is provided a pharmaceutical composition comprising naltrexone or a metabolite thereof or an analogue thereof, for use in the treatment of cancer within a subject, wherein a therapeutically effective amount of the naltrexone or metabolite thereof or analogue of either is to be administered to the subject in a first treatment phase, wherein after the first treatment phase the subject is to be administered a therapeutically effective amount of a cannabinoid in a second treatment phase.
