Cancer.net does a nice job of summarizing how cancer research gets published and how to understand and interpret the results from research studies. In addition, they offer a list of questions to ask when evaluating medical new stories.
You might also consider using a non-partisan fact-checking site, such as SciCheck, which "focuses exclusively on false and misleading scientific claims that are made by partisans to influence public policy."
The UC-Santa Barbara Library has compiled a great list of free publicly accessible databases:
For a research topic related to cancer, the following databases would be most helpful: