I thought at the time the Kings illness was first revealed, it was a benign prostate condition, and the cancer was something else discovered at the time of the operation.
So not prostate - because if it had been that, as it was known he’d had prostate issues (announced to spread awareness) then there’s no reason to hide if it proved to be cancer.
Other cancers can be managed so that they are chronic conditions that are not life-threatening; various blood cancers - including the bone marrow cancer that one source said was something ER II had, but was living with - sprang to mind, but I’ve no idea what the treatment (initial stabilisation and long term control) would be like. Are there others?
I read somewhere that knocking back to a manageable chronic condition was an aim in the development of treatments of some cancers. Can’t remember which though.