A New Mode of Cancer Treatment

The adaptability of cancer makes me think it's in fact a parasitic distributed lifeform, similar to fungus, that turns cells into zombies.

Cancer is your cells though, that's the problem.

Usually, yes. But there do exist infectious cancers that spread between individuals. One is the face cancer that's been killing Tasmanian devils[0]... it started in one individual and spreads to others when they fight (biting each other). Apparently there's a similar (although rarer) cancers that's sexually transmitted between dogs.

[0] https://en.wikipedia.org/wiki/Devil_facial_tumour_disease

Isn't it more like dead cells that are being reawakened, switching to fermentation to create as much NAD+ as possible to grow as fast as possible?