you just came off cancer.. i wouldn't touch hormones right now or anything that can potentially grow cells. the research is sketchy and i cannot point you to anything proving this but trust me i beleive this to be true. its only common sense that you still have cancer cells in your body that are ripe to grow and hormones could ignite them.
you will need a pct if you run sustanon for 20 weeks. 125mg a week will 100% suppress your natural testostone. if anything you should seek the advice of a TRT doc and make sure he is aware of your cancer history and then you need to make a decision if you want to go on TRT and risk getting cancer again.. if i was in your shoes i would probably go the TRT route and take the risk but i would also be checking in with the cancer doc constantly and the first sign of cancer growth i would stop all the hormones immediately
what was the reason for you getting cancer at such a young age anyway? that is very unusual and obviously you are prone to it for whatever reason. not sure if you were exposed to carcinogens or what