MrDocat said:
Why this still happen? After years of research all we can do for a cancer pacient is... nothing? The same we would do 500 years ago?
Unfortunately, cancers are extremely difficult diseases to treat. Because they are a patient's own cells with slight mutations, almost everything that kills cancer cells, kills healthy cells too.
With modern medicine, the 5 year survival rate for many tumors is extremely good (prostate cancer, for example, has a >95% 5 year survival rate). Other tumors have not met with much progress (glioblastoma multiforme has <3% 6 year survival rate, this is owing to the difficulty of getting cancer medications to penetrate the brain tissue).
However, with multiple tumors the difficulty of treating successfully rises dramatically. Often drugs for one cancer are ineffective against another cancer, or even the same cancer at a different location in the body. Using multiple different drugs increases the side effects, often to the point where even if the cancer were cured, the patient can no longer survive.
MrDocat said:
Any particular reason we can't remove all tumors manually/mechanically?
Many tumors can be removed through surgery. Unfortunately, many bone cancers cannot be surgically removed (they would have to remove the entire bone, and this is simply not possible for some bones). For lungs and kidneys, if it is only present in one, rather than both of either organ, it can (relatively) easily be removed. When it has spread to both of either kidney or lung, a person cannot survive the removal of both without at least one transplant, which they will not likely give to someone who's cancer has spread to so many other organs.
Kidney cancers tend to respond poorly to both chemotherapy and radiotherapy, and many chemotherapy drugs are toxic to the kidneys as well (which are likely already damaged from the cancer).
Cancers that are spread over large areas of the body are also difficult (though not always impossible) to treat with radiotherapy, as too much healthy tissue is irradiated in the process.
Sorry I can't give you the answer you want.