Yet another study has found that colorectal cancer incidence rates are rising among young and middle-aged adults -- two age groups that don’t currently undergo regular screening for the potentially fatal disease.

The study, led by the American Cancer Society, found that younger adults born in 1990 have double the risk of developing colon cancer as those born around 1950. They also have quadruple the risk of rectal cancer.

Several studies in recent years, including some performed in Canada, have suggested that colorectal cancer rates are on the rise in young and middle-aged adults, with rectal cancer rates increasing particularly fast.

And while the majority of rectal cancer diagnoses are still in patients over age 55, three in 10 diagnoses are in patients younger than 55.

Rebecca Siegel, a public health researcher with the American Cancer Society who led the study, says the finding that the colorectal cancer risk for millennials has risen is sobering.

“Trends in young people are a bellwether for the future disease burden," said Siegel in a statement.

She said the findings suggest that doctors and the public need to be made aware about the increased rates, “to help reduce delays in diagnosis, which are so prevalent in young people.”

Know the symptoms

“A big problem is that younger patients are much more likely to be diagnosed with a distant stage of the disease and that’s partly because cancer just isn’t on the radar of people in their 20s and 30s and they don’t even know what the symptoms are,” Siegel said in an interview on CTV News Channel Tuesday.

“But it’s also because primary care physicians aren’t following up on these symptoms in young patients because they aren’t thinking about cancer either.”

If someone believes they are experiencing symptoms, Siegel suggests getting checked out by a doctor, and following up.

“It probably isn’t cancer, but it’s best to rule it out,” she said.

The Canadian Cancer Society says symptoms can include:

  • diarrhea
  • constipation
  • stool that looks narrower than usual
  • feeling like the bowel is not completely empty after a bowel movement
  • blood in the stool (it can be bright or very dark red)
  • bleeding from the rectum
  • gas, cramping, bloating and feeling full
  • pain or discomfort in the rectum
  • a lump in the abdomen or rectum
  • fatigue and weakness
  • anemia, which may cause fatigue and shortness of breath
  • nausea and vomiting
  • loss of appetite
  • weight loss
  • blockage in the intestine (called bowel obstruction), which may cause pain in the abdomen
  • a tear or hole in the intestine (called bowel perforation), which may cause widespread infection (called sepsis)
  • frequent urinary tract infections
  • swollen lymph nodes
  • enlarged liver (called hepatomegaly)
  • jaundice (a condition in which the skin and whites of the eyes become yellow and urine is dark yellow)
  • buildup of fluid in the abdomen (called ascites)
  • pain in the abdomen, buttocks or leg
  • breathing problems

Reduce the risk

Siegel said that public education campaigns are also needed to encourage healthier eating and more active lifestyles, “to try to reverse this trend."

The risk for colorectal cancer increases with age, but several lifestyle factors have been linked to the disease, including eating a diet high in red and processed meats, a lack of dietary fibre, a lack of physical exercise, obesity, alcohol, and smoking.

Overall, colorectal incidence rates have been declining in the United States and Canada for decades, with most of the drops driven by increased cancer screening.

Recently though, studies have reported increasing colorectal cancer incidence in adults under age 50, for whom screening is not generally recommended.

Siegel said that people with a history of colorectal cancer, or who have a parent or sibling who has had an adnoma (benign tumour) should actually begin screening at age 40. “A lot of people don’t realize that, so really, more people should be screened than are.”

However, she noted that the increase is happening “not for people who are at increased risk, but just for sporadic cases,” she added.

Dr. John Marshall, a professor of medicine at McMaster University in Ontario, told CTV News Channel that physicians should take a closer look when people at that age come to them with those symptoms.

“I don’t think this is common enough in younger adults to say that we should be routinely screening people in their 20s and 30s for colon cancer, but what it does mean is that we should perhaps have a higher index of suspicion,” Marshall said. “When younger adults come to (physicians) with persistent complaints, we should perhaps take them a bit more seriously and have a lower threshold for other investigation.

Marshall said that it’s important to note that even doubling the risk of colon cancer in a younger population means it is a “rare” phenomenon.

“I don’t think anyone should panic about this but I think it’s observation that can help us figure out colon cancer in general if we can figure out what’s driving this increase in young adults it may give us some insight into what the causes are in older adults as well,” he said.

The study, which appears in the Journal of the National Cancer Institute, found that colon cancer incidence rates increased by one to two per cent a year from the mid-1980s through 2013 in adults aged 20 to 39. In adults 40 to 54, rates increased by 0.5 to one per cent per a year from the mid-1990s through 2013.

Rectal cancer rates in adults who are 55 and older have generally been declining for at least 40 years. But among younger adults, rectal cancer rates have been increasing even faster than colon cancer rates.

They rose about three per cent per year from 1974 to 2013 in adults aged 20 to 29 and from 1980 to 2013 in adults aged 30 to 39. In adults aged 40 to 54, rectal cancer rates increased by two per cent per year from the 1990s to 2013.

Given the numbers, the authors suggest that it may be time to reconsider the age at which to begin colorectal cancer screening for people at average risk.