'RHOBH' star Teddi Mellencamp's tumors have 'significantly shrunk' as she fights Stage 4 cancer

Mellencamp, 43, held back tears on Wednesday as she shared an update with her millions of followers on social media.

"I just finished with all my scans, and my tumors have significantly shrunk, which doctors believe means that this all will work and that I will be back to myself and feeling good," Mellencamp said. 

She added, "I'm going to keep a positive outlook because that's the way my doctor just spoke to me." 

Mellencamp wrote on her Instagram Stories, "All tumors (metastasized melanoma in my brain and lungs) shrunk or disappeared, so I have 6ish more weeks of immunotherapy and my doctors believe I will be healed if everything stays on course."

The reality star revealed earlier this month that life expectancy rates for cancer patients have been on her mind while she is undergoing immunotherapy for treatment.

She was initially upset to hear that immunotherapy has a "50/50" success rate.

"It's one of my favorite things to ask: 'How long I got? What are my chances?' And they oftentimes say 50/50," she said. Mellencamp remembered telling the doctor, "50/50? I wouldn't buy a car that's only gonna drive 50% of the time. I don't want this."

She added, "And [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."

Finding the positive has been a challenge at times.

"I really like to have control, and this is completely out of my control. And for the first time, I'm really scared," Mellencamp said.

The podcast host shares three children with her estranged husband, Edwin Arroyave - Slate, 12; Cruz, 10; and Dove, 5.