About new drugs for treating brain cancer

Regarding the new drug for treating brain cancer, former President Carter's brain cancer shrank and disappeared, which he attributed to the new drug "Keytruda", which is another example of this new cancer drug that enhances the immune system winning against tumors. However, the cost of this new drug is extremely high.

While most immunotherapy drugs boost the immune system to fight cancer cells, Keytruda is the first drug to take a different approach; it blocks a trick that tumor cells use to evade the body's immune cells.
Keytruda, whose scientific name is pembrolizumab, is mainly used to block the interaction between the PD-1 and PD-L1 genes of tumor cells. The interaction between these two genes allows some tumors to escape detection and annihilation by immune cells. The PD-1 gene can prevent immune cells from mistakenly attacking healthy cells. When immune cells appear, tumor cells will cause the PD-L1 gene to activate the function of PD-1. The new drug Keytruda can block the aforementioned "enemy-masking" mechanism, allowing immune cells to function and eliminate tumor cells.
Carter, 91, announced to churchgoers on Sunday that his most recent checkup showed his tumor had completely disappeared, an unusual but not unheard-of situation. Carter has stage 4 melanoma, meaning the cancer has spread throughout his body, a condition that is almost never cured. Even in stage 4, after treatment, the tumor cells can shrink to the point where they can no longer be seen by scanning machines, but they often recur.
The Federal Food and Drug Administration (FDA) quickly approved Keytruda for sale in 2014 for the benefit of advanced cancer patients like Carter. According to a large-scale study, Keytruda can shrink tumors by up to 90% in about one-third of patients. California resident Cathy Thomas is one of the beneficiaries. She said: "I am lucky that I have no side effects." But this new drug costs $150,000 a year.
The report said no one is sure why not every patient benefits from the drug, but it may be because different tumors use different tricks to evade the immune system and chemotherapy drugs. Meanwhile, Li Chitanfei of the American Cancer Society said Carter also received radiation therapy to the brain and had surgery to remove a liver tumor.