I'd wait then kill myself. Think of how much delusional you need to be in order of going through chemotherapy and radiation "treatments". the amount of opioid pills.
Some cancers are not aggressive, but slow-growing to the point of doctors just observing it periodically. It's an umbrella and varies by organ affected too, these are still rare though.
So for the most part, I wouldn't do anything, letting life run its course, even if there's any intervention, I would still be stuck at a quick downward spiral where its final station is an agonizing death. Constant infections, bowel issues, nausea, vomiting, drug induced alopecia, fatigue, and even peripheral neuropathies just to die or for the cancer coming back, stronger and already in metastasis.