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(WGN) — There are no screening tools to detect pancreatic cancer before the disease spreads, and traditional therapies provide months, not years, of survival. But in rare cases, patients can live longer – with the help of their own immune system.

Craig Warner spent much of his life in the air. But the former military-turned-commercial pilot is just as comfortable on the water.

“There’s a lot of parallels between flying and sailing,” he said. “I sailed a little in high school and was always intrigued with it… Ended up buying my own boat and have been racing ever since.”

This past summer, Warner and his team won their division in a race – but he said he shouldn’t have been on the boat.

“I woke up and I had chest pains and I go, ‘Oh, is this the big one?’” he said.

His heart checked out just fine. But his lungs and lymph nodes did not.

The cancer that started in Warner’s pancreas was already on the move when he was diagnosed as stage 4 back in 2018.

Traditional chemotherapy failed. But, fortunately, the tumors exhibited a specific characteristic: a biomarker called MSI High that’s found in only 1-2% of pancreatic cancer patients.

“We know if you are MSI High you have a great chance of responding to immune therapy,” said Dr. Dean Tsarwhas, an oncologist with Northwestern Medicine. “But if you don’t check for it you don’t know.”

As researchers identify more biomarkers, patients may benefit from targeted therapies that help the body’s own immune system destroy cancerous cells.

“It’s out there. The problem is people aren’t often being tested for it,” Tsarwhas said. “Unfortunately, it doesn’t help everyone. But for those it does, it helps for a long time and does great work.”

In Warner’s case, his cancer responded well to a drug known as Pembrolizumab. He received infusions regularly for two-plus years.

“The CT scans from a year ago showed no cancer and I have not shown any cancer since,” he said.

If he didn’t have the rare biomarker and the test to detect it, what would his prognosis have been?

“Typically less than a year,” Tsarwhas said. “Sometimes less than six months is the average survival for pancreatic cancer, stage 4.”

The treatment allowed the 69-year-old to reach a milestone. He walked his daughter down the aisle at her wedding last fall.

“I’m living proof this shouldn’t have happened,” Warner said. “They gave me less than a year when I was diagnosed.”

With his poor prognosis in the distance, Warner said he’s sharing his story with the hope it will inspire other cancer patients to undergo tumor biomarker testing.

“This immunotherapy is still new and maybe people don’t know about it. And I want them to know about it. There is hope,” Warner said.

Doctors said it’s important to have any tumor tested for various biomarkers in case there is an immunotherapy drug that might work against the cancer.