How can oriental medicine claim to cure cancer?

TCM for cancer. What you refer as oriental medicine is traditional chinese medicine correct? Tcm has thousand years history to support its effectiveness and efficacy. A lot of "western" chemotherapy are originally found and made from natural source-i.e.Such as sea cucumber, periwinkle plant. Etc. The problem is that it is really hard to prove/explain the mechanism/ efficacy of tcm using the western standard.