We are currently in the WTF is going on here phase. $5 of anti-fungal medication cuts some cancer death rates in half? Is a tiny amount of fungus in cancer tissue driving growth and metastasis? Does Terbinafine have some other anti-cancer mechanism?
I read an interesting hypothesis that many cancers can be treated by changing (perhaps unpredictable) variables in the patient's body.
We already know cancers thrive in nutrient-rich environments and that many tumors have a narrower set of survival conditions than the normal tissue around them. That's why chemo works: you start to kill the whole person and the tumor (hopefully) dies first.
So what if you just randomly messed around with the conditions of the body? Give someone a diabetes drug, change their diet, add an antifungal... we've seen random successes like this, and the unifying theory might be that the cancer was thriving because it had exactly the right conditions, and now we can change them to cause the cancer to stop thriving.