How Valerie Harper Survived a Fatal Cancer Diagnosis: 'It's a Miracle She's Still Here'

On a recent afternoon, Valerie Harper kicks back on a sofa in her Santa Monica, California, condo overlooking the Pacific, happily chewing gum and talking matter-of-factly about the disease that should have killed her four years ago.

“I’m still here,” Harper tells PEOPLE in an exclusive interview in this week’s issue. “I still have cancer, but I’m okay and most of my days are good.”

Nearly a half century has passed since Harper made her debut as Rhoda Morgenstern on The Mary Tyler Moore Show, a character that gave the actress her own hit sitcom, Rhoda, and made her a 1970s icon.

But in 2013, Harper made headlines for something that had nothing to do with acting when she revealed in the pages of PEOPLE that she’d been diagnosed with leptomeningeal carcinomatosis — a condition that occurs when cancer cells spread into the fluid-filled membrane surrounding the brain, known as the meninges.

At the time, she’d been given three months to live.

Now, over four and a half years later, Harper continues to defy the odds and remains as perky, funny and as youthful as ever.

“It’s a miracle she’s still here,” says her oncologist, Dr. Jeremy Rudnick.

Doctors put Harper on what was then a relatively new chemotherapy drug shortly after her diagnosis and the disease was kept in check. But earlier this year she began experiencing seizures and cognition problems and her doctors found an experimental drug that has once again begun working.

“Valerie developed this disease at a time when we keep coming up with stronger and better targeting drugs for her particular cancer,” adds Rudnick. “The longer we keep her alive the more options we have.”

Harper is grateful for the medical breakthroughs that have kept her alive, but acknowledges that the secret to her survival has been her husband of 30 years, Tony Caccioti, 78, a former personal trainer to the A-list who has become her devoted caregiver.

“He’s such a nudge,” says the four-time Emmy winner who continues to tackle the occasional acting gig—recently taping episodes of The Simpsons and American Dad, and playing a woman with Alzheimer’s in the short film My Mom and the Girl.

“He does everything for me, drives me everywhere, makes sure I’m eating healthy, walking and lifting weights. Really, he’s the best nudge in the world.”

For more on Harper, pick up this week’s issue of PEOPLE