Lifestyle changes for one.

Do you smoke? quit smoking. Do you live in areas with lots of air polution? High levels of radon where you live? Move.

Do you work with a bunch of carcinogenic chemicals? Find something else to do.

You can also get a gene test do see if you're suspectable to certain cancers.

But most importantly: listen to your body. If you feel that something is wrong, take it up with your doctor.