treatment of terminal cancer patient

Shalom Harav Halperin   

Thank you for your time and guidance in the matter of
The lady in ICU with Cancer and brain damage.
Please send me the Guide in English for the ICU terminal
Patients.   
I understand from your answer that the Doctors must
Continue to give food,water,oxygen,and antibiotics.
They however don’t have to treat her aggressively beyond that.
Please clarify if they DON’T Have to OR that they SHOULDN’T?

Toda Raba