Okay let me explain this from a Doctor’s view:
We would make a pain control plan for each patient, but naturally every human is different and reacts differently to cancer.
Mostly, we would choose Morphine to moderate cancer esp in stage 4. (End-stage cancers.) But some patients do not tolerate morphine as they suffer severe adverse side effects, although this is rare. Sometimes some patients refuse it due to their beliefs. If allergic, we try Demerol, katamine, fentanyl etc. There are many other alternative meds.
Sadly in stage 4 cancer the realism is the patient is dying. It is an immune system disease and there will be a point where you won’t be able to fight it anymore. The body will naturally prepare for the final breakdown and these stages are tough on all cancer patients. No medicine can prevent your body from preparing its breakdown and dying as there is no cure for cancer yet.
There is hell lot of difference between stage 4 cancer and terminal cancer. A stage 4 cancer patient may be totally pain free, walking about without anyone noticing any thing worng. In certain cases stage 4 cancer is curable.