Modern medical science enables people to survive diseases that would kill them even just a few decades back. We have modern medicine, treatments for cancer, and transplants. Specifically about transplants, there are many different types of transplants. So you have blood transfusions, heart transplants, lung transplants, liver, kidney, and so on. You can now even transfer limbs to people. In an ideal world, there will be enough donors to make sure that whoever needs a transplant for medical reasons gets one; however, this is not the case. It is not easy to get enough donor organs, and hence hospitals and people needing donors are pretty desperate. There was a case earlier where a patient got an organ from somebody who had a severe disease, and the patient died soon after. Here is another case (link to article):
A leading UK hospital has defended its practice of using organs donated by smokers after the death of a soldier who received the cancerous lungs of a heavy smoker.
Corporal Matthew Millington, 31, died at his home in 2008, less than a year after receiving a transplant that was supposed to save his life at Papworth Hospital -- the UK's largest specialist cardiothoracic hospital, in Cambridgeshire, east England.
Papworth Hospital released a statement saying using donor lungs from smokers was not "unusual."