I suggest looking into hyperthermia therapy (which is used in combination with immune system priming drugs, and sometimes traditional chemical/radiation treatments)

Unfortunately the classic easy external way it’s done isn’t the best fit for brain application, as it’s literally heating the body up in a sauna to a point where heat reactive proteins are generated. This forces the cancer to either open up various cellular transport mechanisms (announcing itself to the immune system) or denature (and die). This is repeated multiple times, and can actually be so effective and the doctor overseeeing the treatment needs to be careful not to kill off too much cancer at once if there is a large amount, due to the resulting necrosis.

However related to this for deep body use is using radiation devices or probes to heat tumorous areas deeper in the body, or outright use laser probes to not-quite-burn places. This can allow access to otherwise inoperable tumors. See Laser interstitial thermal therapy (LITT)

https://www.barnesjewish.org/Medical-Services/Neurology-Neur...

https://my.clevelandclinic.org/health/treatments/17114-hyper...

Hyperthermia therapies are lesser known for some tragic reason, but they are FDA approved.