After experiencing unusual symptoms that are typically unrelated to cancer, a 47-year-old athlete – a lifelong non smoker – tragically lost his life to a fast-moving, aggressive form of lung cancer – a devastating diagnosis no one saw coming.

When Chad Dunbar was 45, the endurance athlete – who had never touched a cigarette in his life – was in the best shape he’d ever been. Known for clocking over 3,000 miles on his mountain bike through the rugged landscapes of Colorado and Utah, Dunbar was the picture of health and resilience.

But in 2023, that image was shattered.

Unexpected pains

After completing a grueling cycling challenge in the mountains, Dunbar began feeling unexpected pain and swelling in one of his calves. At first, he thought it was a muscle strain from overexertion. But what seemed like a simple sports injury turned out to be something far more sinister.

“The nurse came in…she’s like, hey, we think you have lung cancer. Man, there’s no way – no way I’ve got lung cancer. I was doing 3000 miles on my mountain bike every season and my lungs are probably the healthiest piece of me,” Dunbar said in a moving Instagram clip where he shares his journey after he was handed a life-shattering diagnosis of terminal lung cancer.

Describing his reaction, the father of two shared, “It was surreal. It was denial. It was pissed off…Get mad… How? Why?”

But the diagnosis was real. And it was terminal.

Rare genetic mutation

Dunbar, a loving husband and devoted father of two boys, was stunned. So was his family – the super active man appeared to be the epitome of health.

“NO, he was never a smoker. He didn’t work in a mine. He’s lived in clean-air Colorado and Utah,” his brother-in-law, Jordan Reynolds, writes in a Facebook post. “Chad was in the best shape of his life when the Stage 3 [now stage 4] lung cancer showed up at age 45. He was a legit athlete.”

Leading cause of lung cancer

According to the Centers for Disease Control and Prevention (CDC), smoking is the leading cause of lung cancer in the U.S., responsible for 80% to 90% of related deaths. But rare gene mutations like RET can still trigger lung cancer in lifelong non-smokers.

It’s aggressive, fast-growing, and often spreads silently before it’s even detected.

Quickly spread

Doctors soon discovered that Dunbar’s cancer was caused by RET – a rare genetic mutation – that often present with vague or misleading symptoms – like leg pain or swelling – making early diagnosis especially difficult.

And by the time Dunbar’s cancer was discovered, it had already spread – to his brain, liver, bones, and lymph nodes near his heart.

‘Big improvement’

After his shocking diagnosis, Dunbar initially responded well to an aggressive treatment plan. Doctors prescribed a combination of targeted therapies – designed to attack cancer cells carrying the RET mutation – along with standard chemotherapy, the Daily Mail reports.

And, for a while, it looked like the tide was turning.

“Big Improvement,” Dunbar said about his scans in the summer of 2023. “I had six spots in my brain that went down, three spots of my ribs they couldn’t find, spots of my liver had gone down, and the main tumor in my lung had continued to shrink.

“I’m thinking, ‘man, I’m feeling good.’”

But RET-positive lung cancer is relentless.

‘Passenger mutation’

In March 2024, Dunbar shared a heartbreaking update. A new “passenger mutation” had developed in his brain and liver – changes that made treatment even more difficult. Doctors gave him just a 5% chance of surviving more than five years.

Faced with devastating odds, Dunbar refused to let fear win: “My doctors gave me a 5% chance living over five years,” he said.

After allowing himself a “pity party,” he decided to fight and “enjoy every minute” he has with his sons Walker and Noah, and wife Allyson.

Dunbar adds, “Hey, you know what? Freaking 5%, I’ll take those odds. Every day is a battle. Hang on for one more day.”

Dunbar dies

Sadly, on June 25, 2025, Dunbar’s battle with cancer came to an end.

According to a tribute shared on Ever Loved, “After his final appointment in mid-June,” the family was told “the cancer had spread rapidly and that treatment would no longer be effective.”

“To know Chad was to love Chad. His smile, dimples, and genuine interest in others were what you noticed most. Tall, brown-eyed, and known for his thick, beautiful brown hair, Chad was incredibly handsome, funny, smart, and kind. He was only 47, and way too young,” the message shared.

His heartbreaking story serves as a powerful reminder that lung cancer doesn’t only affect smokers. As his loved ones grieve the loss of a vibrant, athletic man who defied every cancer stereotype, they continue to raise awareness about the lesser-known symptoms and genetic mutations that often go undetected until it’s too late.

If you or someone you know is experiencing unexplained symptoms – even if you’re fit and healthy – don’t ignore them. Early detection can save lives.

Please share Dunbar’s story to honor his memory and help others recognize that lung cancer can happen to anyone.