I'm sorry to hear about your neighbor'* illness. Seems to young and too healthy to be in that situation but cancer has no concern for age, sex, race, social level, ect.
My mother died as a rusult of cancer in 1979 and my father died a little over 3 years ago from lung cancer. His illness was not nearly as sudden, though. He managed to survive a couple of years with treatment but sometimes I thought the treatment was worse for him than the actual cancer.
Out thoughts will be with him.