dark room with hospital beds
August 9, 2017

Younger people are dying of colorectal cancer, but nobody knows why 

For several years, rates of colorectal cancer have been rising among Americans aged below 55. This could be put down to better detection, but the revelation that deaths from that disease are also increasing is particularly worrying.

For decades, screening has started at age 50, meaning colorectal cancer should be better detected and prevented. This makes the results of a new study, showing higher deaths as well as higher rates, more concerning.

"This is not good news. We looked at adults from ages 20 to 54 and following several decades of pretty rapid declines in death rates, over the past decade deaths in this age group have been increasing," lead investigator Rebecca Siegel, strategic director of surveillance information services at the American Cancer Society, told CBS News.

"This indicates that there's actually a true increase in disease. It's not just detection of disease that was there and that we're catching it earlier."

Experts used data from the National Center for Health Statistics to look at colorectal cancer deaths in people aged 20 to 54 from 1970 through 2014. The study is published in the Journal of the American Medical Association.

Racial differences rule out lifestyle factors as major culprits

The study also looked at racial variations in colorectal cancer. Although African-Americans continue to be more likely to die from colon cancer than other demographics, the rates among this group have actually declined. White men and women, it appears, are driving the increases that have been noted.

While they remain possible factors, risks for colorectal cancer like obesity and sedentary lifestyles are not thought to be playing a hugely significant part, given that they exist across both demographics, which is baffling experts.

"The thinking has been that the reason we're seeing the increase in this disease is because of the excess body weight we've been dealing with for the past several decades, but the obesity epidemic has affected everyone universally across races and ethnicities and if anything the increase in obesity in the black population has been higher," Siegel said.

"...no one really knows why this is happening," she added.

We need to understand bacteria better

One possibility is that the increase is related to microbiome bacteria, which usually thrive in humans.

"We're learning more and more all the time about how important the balance of the microbiome is, particularly in the colon and how that relates to health," Siegal said. "I think we're going to need more time for etiologic studies to try to understand this."

Siegal explained that this type of cancer in people under 55 is still rare, but that screening and keeping an eye out for symptoms - including abdominal pain, blood in the stool, weight loss and changes in bowel patterns - is advisable.