Nobody ever wants to hear they have cancer, but when it strikes a young person, the news is perhaps even more devastating because everything about the future they were imagining and working toward is thrown into question.

Unfortunately, early-onset cancer ? disease in people younger than 50 years old ? is being diagnosed more frequently, according to various studies. And among early-onset cancers, colorectal cancer hovers near the top of the list.

?It was shocking to see that a young person ? perfectly fit and healthy, no risk factors, no family history ? could be diagnosed with Stage 4 disease. And then it just became more and more common, which is also distressing,? Dr. Kimmie Ng told CNN Chief Medical Correspondent Dr. Sanjay Gupta recently on his podcast, Chasing Life.

Ng, a gastrointestinal oncologist and associate professor of medicine at Harvard Medical School, has been treating patients for two decades at Boston?s Dana-Farber Cancer Institute, where she is the founding director of the Young-Onset Colorectal Cancer Center, one of the nation?s first centers that treat younger adults with the disease.

?It?s difficult to receive a cancer diagnosis no matter what age you are, but younger people face really different challenges,? Ng said. ?Eighty percent have children under the age of 18. They?re also caring for elderly parents. They?re in the midst of their careers. Some people are still getting education. Some people are still planning to expand their families.?

Early-onset colorectal cancer is already the leading cause of cancer-related death in the US in men younger than age 50, and if the trend continues, Ng said, it will become the leading cause of cancer death in women under 50 by 2030. (After breast cancer, colorectal cancer is the second leading cause in younger women now.)

She points out, however, that in absolute numbers, these cancer cases in younger people are ?still quite small,? noting ?it is still relatively rare to develop any of these cancers at a really young age.?

Screening is key

Across all ages, colorectal cancer cases and related deaths in the US have been declining for decades, Ng said, attributing that success to improvements in treatment and public health efforts to promote screening. ?But that benefit has not been seen in people under the age of 50,? she said.

In 2021, the US Preventive Services Task Force, an independent board of medical experts, lowered the recommended age to start screening for colorectal cancer in asymptomatic people of average risk from 50 years old to 45.

But Ng doubts the panel will lower the age again soon, noting not only the relatively small absolute numbers but also other factors that go into implementing a successful screening program, such as cost and the risks associated with screening, including bleeding, sedation complications and false positives.

Instead, Ng believes the focus should be on figuring out why this surge in early-onset colorectal cancer is happening. ?What are the risk factors?? she said. ?Who is at risk, and can we tailor that high-risk 30-year-old for earlier screening??

Also important: More people need to get screened.

?There was this effort to get 80% of the population screened in the United States, but we haven?t yet reached that goal,? Ng said. ?And so it is really important that we continue public health efforts to really advocate that screening can be lifesaving and it really needs to be done.?

What do you need to know about early-onset colorectal cancer? Ng shares five things that matter.

Know the early signs of colorectal cancer

Many types of cancer are rising among young people around the world, Ng told CNN via email, but cancers of the digestive system are rising most rapidly. That includes colorectal cancer, pancreatic cancer, gastric cancer and biliary tract cancer.

Early detection is critical. And knowing the red-flag symptoms associated with colorectal cancer is essential, Ng said.

For young people ? the most predominant presenting symptom is seeing blood in the stool. For example, if you see blood that?s actually mixed into the stool rather than sitting on top of it or in the toilet bowl or just on the toilet paper. If it?s mixed in the stool, that?s perhaps a little bit more concerning and a little bit more characteristic of a malignant cause.?

Unintentional weight loss is another red-flag symptom, Ng added.

Other common symptoms include prolonged changes in bowel habits, such as new diarrhea or new constipation, thinner stools and abdominal pain. In addition, fatigue could indicate anemia or low red blood cell counts.

No matter how uncomfortable these conversations might be, Ng said it is crucial to discuss any changes in bowel habits with your doctor.

?The increase in young-onset cancers is generational, with every generation after 1950 experiencing rising incidence,? she said.

?For example, someone born in 1990 now has >4x (greater than four times) the risk of developing rectal cancer and >2x (greater than two times) the risk of developing colon cancer compared to a similarly-aged person who was born in 1950.?

?When we see these ? effects, what it usually suggests is that there?s some environmental exposure or exposures that have happened recently that are contributing to that rise,? Ng told Gupta on the podcast. ?So, the big question now is what are these things that are actually leading to this increasing incidence in young people??

Researchers have been trying to pinpoint the drivers of this unsettling trend.

?The cause of the rising rates of young-onset cancers is thought to be due to environmental factors,? Ng said, noting that our genes could not have changed so much in 30 years to be the culprit.

Environmental factors might include obesity, sedentary behavior, and diets that are high in red meat, processed foods, added sugar and sugar-sweetened beverages.

?The leading hypothesis has been obesity,? Ng told Gupta, adding that the obesity rates in the US, which ?have been skyrocketing in recent decades,? seem to parallel the rise in young-onset gastrointestinal cancers, which include colorectal cancer. Obesity increases body-wide inflammation, which can set the stage for precancerous changes.

Nevertheless, Ng said, most younger colorectal cancer patients she and her colleagues are seeing are not obese. ?Many are marathon runners, they?re triathletes, they?re eating really healthy, they eat organic ? and yet they?re still being diagnosed with young-onset colorectal cancer.?

The influence of other environmental factors are still being studied, Ng said, citing microplastics as one example. Exposure to toxins and diet in the first decade of life can also affect the microbiome, allowing certain cancer-promoting microbes to take hold.

?We are still in our infancy in understanding whether those are true risk factors, whether there is a link and actually how do they actually lead to cancer, in terms of these biological mechanisms.?

Genetic testing may offer insight

Most cases of early-onset cancer are not explained by a heritable factor, but Ng said those diagnosed with any cancer at a young age have a higher chance of being diagnosed with a hereditary syndrome, such as Lynch syndrome or familial adenomatous polyposis.

?All young patients diagnosed with cancer should undergo familial genetic testing,? she said.

It is also important to know your family history of cancer, Ng said. ?If there is a family history, then an individual may be eligible for cancer screening, or eligible to start cancer screening at a younger age, and this could be life-saving,? she noted.

Younger patients may have a harder time

If you have been diagnosed with any cancer, being young has its advantages, Ng said. Younger patients tend to be healthier, for one. They are more likely to withstand higher doses and more cycles of chemotherapy compared with older patients, and they can undergo surgery and radiation more often as well.

Nevertheless, Ng, said, ?their survival is not necessarily better than that of an older patient with cancer.?

She noted that for colorectal cancer, ?the very youngest patients? ? those younger than age 35 ? ?seem to have shorter survival.?

Again, tilt the odds in your favor. Get screened

Ng reiterated the importance of screening at the appropriate age for your level of risk: 45 if you are of average risk, and earlier if you have a family history.

She also stressed how crucial it is to put embarrassment and stigma aside and to reach out to your doctor, and even a family member, if you are having unusual symptoms, like those mentioned above.

?It?s so important that we try to normalize these conversations,? she said.

She added she also would like to see physicians routinely and systematically ask their patients two questions: ??Are you having blood in the stool? Are you having a change in your bowel habits?? so that these symptoms can come to light.? Especially because many people are reluctant to bring them up themselves.

EDITOR?S NOTE: To learn more about early-onset colorectal cancer, listen to the full episode here. And join us next week for a new episode of the Chasing Life podcast.

CNN Podcasts? Kyra Dahring contributed to this report. (CNN)

?It?s crucial to put embarrassment aside and talk to your doctor about unusual bowel symptoms. SDI Productions/E+/Getty Images)

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