John Mellencamp shares heartbreaking side effect of Teddi's cancer

John Mellencamp is sharing how he supports his daughter, Teddi, amid her longstanding cancer treatment.

"She's been going through hell the last year," the rocker, 74, told People. "She has 10 lesions in her brain … even though the lesions are not cancerous right now, they still interrupt her thinking, and it's in her frontal lobe."

He shared that he talks to her every day and "every day" as she battles stage 4 cancer.

Teddi has already had some lesions removed, but is getting radiation for the ones that remain.

"The lesions are still there, but the cancer's not," her dad explained. "But that doesn't mean she's home free; it just means right now there's no cancer. So she has to keep on this treatment for who knows how many years."

He also shared that "her personality has changed" due to the lessoins in an area of the brain that controls thinking and emotions, as well as due to the toll of treatment. "She's still the same person, but she's not the same person. It's not fun."

John Mellencamp has also been trying to convince the 44-year-old to move back home to Indiana.

"I've tried to talk her into moving back home," he shared. "I said, 'Move back to Indiana, bring the kids and just come back and live in Indiana,' but she won't do it."