Topical caffeine or EGCG inhibit carcinogenesis and selectively increase apoptosis in UVB-induced skin tumors in mice
Quite a long and biochemicalish title, but gets to the point. I would be surprised if anyone out there has not yet heard about this article. This article does address topical application, but it is very possible that high intakes of tea may also have similar effects. We already know the green tea (which contains high levels of epigallocatechin) has shown to lower many types of cancer risk at levels of 6 to 7 glasses a day.
Lu et al., 10.1073/pnas.182429899