This article on silibinin (also spelled silibin,silybin,silybinin) the major part of silymarin in milk thistle shows activity against Hepatocellular Carcinoma in laboratory cell experiments:
http://clincancerres.aacrjournals.or...act/11/23/8441
Silibinin Efficacy against Human Hepatocellular Carcinoma
This adds an other hint of efficacy of milk thistle extracts againts cancer to the one shown in the first post (by Tom) of this thread on lung cancer