1, whether it can relieve pain has nothing to do with cancer. There is no connection between the two.

2. First of all, painkillers have no therapeutic help for cancer, let alone "treating cancer".

3. Whether the pain can be relieved depends entirely on "drug performance, dosage" and "patient's body".

Finally, the illegal "drugs" in law are actually painkillers. Any painkiller has side effects, such as strong adaptability, easy addiction and increased drug dependence ... That is to say, any painkiller, if used in a certain amount (time), may be adapted by the body (the efficacy is gone and the pain can't be stopped). If you need to relieve pain, you can only increase the dose or replace it with a more powerful drug. In the end, the body can't bear direct death.