Some cancer statistics are missing, as in no one seems to have tracked the issue. One area where statistics are missing is in hormonally-linked cancers in people who are undergoing gender correction treatment.
I've tracked down some good news - both M2F and F2M hormone treatment show signs of being safe in the short term.
The best prevention tip I have here is that everyone needs to advocate that statistics - good statistics - be kept. By cancer prevention/treatment groups, and/or by groups advocating for the rights of transexuals, and/or the CDC, etc. The drug companies can't be trusted. Not all doctors can be trusted.
Yes, this cancer prevention tip is political/activist in nature. It's not going to be the last tip that will be. That's because we as individuals can't do every bit of the scientific research; we as individuals are affected by the environment (air, water, etc) around us; we as individuals need transparency on the part of those that supply our food, our drugs, our cleaning agents, our cosmetics, etc. so we can make informed choices. I don't think that these things will happen without consumers banding together and getting the government to force disclosures, to force companies to not pollute, and to put money into science research.
Incidentally, Libertarians out there - I think it's section 8 of the US Constitution that authorized Congress to promote scientific research. Just thought you'd like to know.