A mom in her 30s was diagnosed with stage 3 colorectal cancer after doctors dismissed her symptoms for 6 years

• A mom in her 30s was diagnosed with colorectal cancer after noticing three symptoms.
• Doctors wrote off her symptoms as side effects of pregnancy and childbirth.
• She said a colonoscopy saved her life and could save others, as early cancers are on the rise.

The first red flag for Marisa Peters was literal: blood on the toilet paper.

After the birth of her first child, she noticed symptoms — rectal bleeding, changes to her bowel movements, an urgent need to go — which her doctors chalked up to lingering physical side effects of childbirth.

It took six years until she finally found that the underlying cause of her symptoms was stage 3 colorectal cancer, a shocking revelation for her as she considered herself a young, healthy mom of three.

"I really, really did not expect that cancer was the diagnosis," Peters told Business Insider. "I knew for sure that something was wrong the entire time. I just did not know what."

Now 43 and cancer-free thanks to extensive treatment, Peters is channeling her experience to raise awareness of the rise in young cancer cases among people in their 20s, 30s, and 40s.

The nonprofit Be Seen, which she cofounded with her husband Josh, promotes cancer prevention resources like "poop parties" where people gather to prep for colonoscopies and reduce the anxiety, stigma, and shame.

Peters, who lives in Los Angeles, said she hopes to raise awareness about early colorectal cancer symptoms to help others avoid the challenges she faced.

"I had not even heard about the disease," she said. "The more that I went through treatment, the more frustrated I grew because it's preventable."

Doctors missed the subtle symptoms of cancer

Peters, a Broadway vocalist turned advocate, describes herself as a Type A personality with big dreams and the energy and drive to match.

When she noticed changes to her health after the birth of her first son, she felt the doctor dismissed her concerns as being overly ambitious about her post-pregnancy lifestyle.

"I had high standards and expectations for myself and what I accomplish in life," Peters said. "From a medical practitioner standpoint, that was interpreted as 'This woman has unrealistic expectations of what her body's going to be like after having had kids.'"

The symptoms persisted and intensified over time. She needed to use the bathroom more frequently and more urgently. Her bowel movements looked different, with smaller, ragged-edged stools. She saw blood in her stool more often and in greater amounts, to the point where she developed anemia.

Still, multiple doctors over many appointments said it was normal to feel different after pregnancy and childbirth. She had hemorrhoids, which can cause rectal bleeding, but that bleeding is also one of the most common signs of colorectal cancer.

Peters thought she was too young, but increasingly, people in their 20s and 30s are developing gastrointestinal symptoms that turn out to be colorectal cancers.

Among young patients, cancer is often diagnosed late, when survival rates are lower. For patients with stage 1 colorectal cancer, the survival rate over five years is more than 90%. For patients with stage 4, the survival rate drops to 15%, sometimes less.

Waiting to act on symptoms, even if they're vague, can increase the likelihood of a more serious illness.

"We lost so much time that I don't know if it's miraculous, lucky, or blessed that I didn't have a stage four diagnosis," Peters said.

Colon cancer on the rise in younger patients

Ten days after Peters was diagnosed, she started a treatment plan that lasted nearly a year, including radiation, surgeries, and a dozen rounds of chemo. She managed to keep her energy up enough to work through the process.

The treatment ended with the good news that she was in remission. Then came an unexpected challenge: figuring out her life and identity as a cancer survivor.

"Life never goes back to what it was before the diagnosis. You're irreparably changed," Peters said.

When a cancer treatment ends, there's a sense of relief for friends and family, a feeling that the hard part is over. For patients, remission brings a new set of uncertainties.

Peters said figuring out how to understand her new life and the new realities of her body felt very lonely. She leaned into her newfound experience of navigating cancer diagnosis and treatment, channeling her work as an artist, performer, and leader to bring people together for the cause.

Her nonprofit foundation aims to raise awareness of colorectal cancer symptoms, improve access to preventive screening, such as colonoscopies, and empower people to advocate for themselves. The current recommended age to start colorectal cancer screening is 45.

Peters said if she had waited until then for a colonoscopy, it may have been too late.

"We really want to emphasize the importance of trusting your gut and your body," Peters said. "You know your body best, and you've got to be relentless."