Teddi Mellencamp has been told that she has a 50 percent chance of surviving cancer

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 remain upbeat about her prospects.

She shared: "[The doctor's] like, 'No it's only because that's how long immunotherapy has been around so that's how long the study has worked'. So that's when I then try to find the positive."

Earlier this month, Teddi insisted that she's determined to "beat" cancer.

The reality star - who had tumours removed from her brain and lungs in February and March - made the comment in response to a message from one of her Instagram followers, who observed that stage 4 cancer "is terminal especially with metastasis".

The Instagram follower added: "Praying that Teddi heals and is an outlier."

Teddi subsequently admitted to being saddened by the comments, describing it as "heart-breaking" to read.

Teddi - who has Slate, 12, Cruz, ten, and Dove, five, with her estranged husband Edwin Arroyave - replied: "These kind of comments make me really sad. I know people are trying to help but heart breaking for me to read. (sic)"

Teddi remains convinced that she can overcome cancer.

She said: "Of course I know the chances but I truly believe with my whole heart, I will beat this and watch my kids graduate."

Meanwhile, Edwin previously revealed that he's been "upfront" with their children about Teddi's health battle.

The TV star told Bravo: "I was upfront with them [about] what was going on.

"They got scared, obviously. They were concerned, but I tried my best not to sugarcoat it too much. I let them know, 'Hey, there, there are some risks that come with this.' I called it the way it was."