A 31-year-old marathon runner thought she had norovirus. She was diagnosed with stage 3 colon cancer.

• Katelyn Jonozzo, 31, lives a very active lifestyle and has no symptoms of colon cancer.

• She was diagnosed with the disease in February when she suddenly experienced severe pain and extreme bloating.

• Jonozzo needed an emergency colostomy and adapted to running with a colostomy bag.

Katelyn Jonozzo prided herself on being very active growing up.

Before the age of 18, she practiced gymnastics 4 to 5 days a week. “I like the discipline, I like having a strict schedule,” Joe Nozzo, 31, told Business Insider. “This goes to show how important health and fitness are to your lifestyle.”

In her 20s, she became obsessed with marathons. As a supply chain analyst, Joe Nozzo often wakes up at 4 or 5 a.m. to lift weights and run for two hours before going to work. In 2024, she qualified for the Boston Marathon. She can’t wait to run it in 2025.

That was before she suddenly felt severe pain in her stomach in February.

Jonozzo began experiencing flu-like symptoms and vomiting. She attributed it to norovirus, which was circulating in her Cleveland suburb at the time.

“My belly started getting very, very swollen — I looked like I was going to be pregnant,” Jonnozzo said. “But it’s also a symptom of norovirus, so I just lump it in that category.”

When the pain got worse — a tingling sensation in her sides and constant vomiting — her two best friends urged her to go to the emergency room rather than wait another day. Gionozzo agreed, assuming the worst-case scenario was appendicitis.

After undergoing emergency surgery to remove part of her colon, she learned she had stage 3 colon cancer and a secondary cancer in her abdomen.

Jonozzo said her training mindset helped her cope with her new reality. “I’m definitely a short-sighted person,” she said. “I think I cried for about 30 seconds. Then, I looked back at the doctor and thought, ‘What’s the plan? What are we going to do?'”

Zero warning signs

Jonozzo said she was initially dismissed when she went to the hospital and was told she probably just had stomach pains or bloating. She insists she has a high pain tolerance and would not come in unless it was severe.

Eventually, she got an MRI, which revealed a three-inch tumor on her colon that was about to rupture.

Over the next 48 hours, she underwent an emergency colostomy, in which one-third of her colon was removed and a colostomy bag was installed. “I was in shock, a lot was going on and I really didn’t know what was going on,” she said.

Ten days after recovering from the stress, she learned the exact diagnosis. Jonozzo recalled that her doctors estimated the tumor had been growing for about ten years.

“How about I run a marathon?” she said. “How did I exercise when I had a tumor in my stomach?”

Exercise with a colostomy bag

A few weeks after the surgery, Jonozzo began chemotherapy. At first, she kept a positive attitude: making poster boards with affirmations to place around her house.

“I still didn’t really understand the journey I was about to go through until I said probably about three or four chemo treatments,” she said.

At that time, she began to lose her hair and taste, develop skin changes, develop neuropathy, and lose feeling in her hands and feet. “That’s when I realized, ‘Okay, you have cancer. This isn’t just something we’re going to put our heads down and go through.'”

One challenge is exercise. During treatment, her daily life became impossible. “I definitely have to tone everything down,” she said. She gave up long-distance training and lifting weights in favor of outdoor walks and three-mile jogs.

The biggest obstacle was the colostomy bag. “I was obviously very uncomfortable with the bag at first,” she said. But as she began connecting with other young cancer patients through The Gathering Place support group and the Colorectal Cancer Alliance, she began to embrace the bag.

“I would go to the pool in my bathing suit and take the bag out, or I would lift my shirt up at the gym and let people know the bag was there, and I think that gave me confidence,” she said.

Looking for the positive helps her maintain as normal a routine as possible. “I think it’s amazing that they figured out how to poop your intestines out and you can still go to the bathroom,” she said. “It’s a great device if you ask me.”

She’s running a marathon with a cancer support group

After seven months of treatment, Jonozzo was deemed cancer-free. She completed chemotherapy in August and underwent colostomy recanalization in November. In mid-December, her first screening since completing treatment, she will learn more about her future screening schedule, which she already knows will include twice-yearly colonoscopies.

She will also be officially allowed to exercise after surgery and is eager to get back to her old routine.

“I’m a little nervous because normally I can just pop out and run and do these things, but I have to slowly get back into it,” she said. She plans to run three marathons in 2026, hoping to requalify for the Boston Marathon through one of them.

She’s especially excited about the Cleveland Marathon in May. She will run her cancer fundraising group as captain, which she says has awakened a new passion in her. “I love advocating and talking to people,” she said. “I’ve always loved doing it – I just didn’t have the confidence to do it before.”

She says this is just one of the ways her cancer experience has changed her, making her more present.

“People think I’m crazy for saying that, but I truly believe it’s one of the best things that’s ever happened to me,” she said. “I wouldn’t trade this experience for anything. I really wouldn’t.”

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