the “premise” of this conspiracy theory is that the drug companies already found it, and are covering it up...
Of course for this to be true means that the actual individuals who were involved in the discovery keep their mouths shut...
So, someone discovered the cure in a drug companies lab, the execs decide we make more money selling drugs to treat so lets not make money selling things that cure... so squash the research and kill off the scientists who discovered it, oh, and then to be sure no one ever talks, need to kill off the people who decided to kill off the scientists too...
Honestly, my bet is that cancer treatment will likely end up being like this doctor is proposing... eventually will be like HIV treatment... lifetime of drugs, to keep the cancerous cells in check.. as there is no way to truly guarantee not one single cancerous cell remains.
I think you hit the nail on the head, on both accounts.