A close immediate family member was diagnosed with glioblastoma. The biggest treatment impact was doing the surgery, and they added a localized drug delivery wafer to combat the cancer. She was also on oral chemotherapy and some steroids. Fortunately, she was able to make a full, mostly symptom free recovery for ~5 years until remission that unfortunately could not be treated and took her life. I consider the treatment a success as 5 years was well beyond the expected 1 year mortality on diagnosis.

Please stay away from these clinics promising you the world for half a million. They're taking advantage of your desperation. Your family member is at stage 4 so the prognosis is not good. Continue doing the surgeries and if a drug delivery placement is an option, I'd pursue that. But beyond that, it's likely that your loved one has limited time left, and you're really talking about extending quality of life by possibly a few years.

Enjoy the time you have with them while being proactive on surgical treatment.