United Kingdom, April 11 -- Teddi Mellencamp has been told that she has a 50 percent chance of surviving cancer.

The 43-year-old reality star has stage IV melanoma, which has spread to her brain and lungs, and Teddi has been asking her doctors about her survival chances.

Teddi said on 'Nightline': "It's one of my favourite things to ask is 'How long I got? What are my chances?' And they often say 50/50. 50/50? I wouldn't buy a car that's only gonna drive 50 percent of the time. I don't want this."

The reality star has recently been undergoing immunotherapy, which is a new, innovative form of cancer treatment - but doctors haven't been able to provide her with a clear idea of its success rate.

Despite this, Teddi is determined to remai...