Rebecca Siegel, MPH: Colon Cancer in Young a Global Problem

Editor’s Note: Colon cancer and other gastrointestinal conditions have historically been considered ailments of the elderly. Guidelines even recommend regular testing only for people over the age of 50. Since the mid-1980s; however, investigators have seen alarming results suggesting that colon cancer incidence rates increased by 1-2% annually in adults 20-39 years.

Rebecca Siegel, MPH, Strategic Director, Surveillance Information Services, and her team from the American Cancer Society, used the “age-period-cohort-modeling” tool to dissect trends in colon cancer incidences by generation. Siegel spoke with MD Magazine to discuss their study results.

Did your study findings surprise you?

What was surprising was to see the extent in changed risk. Initially, colon cancer risks started to increase in people born in 1950. Now, results show that people as young as those born in 1990 have twice the risk of colon cancer compared to those born in 1950.

We have previously published on rates of colon cancer in populations younger than 50 in 2009. So, we’ve known for a while that the rates have been increasing in people younger than 50, while dropping in people older than 50. That’s the natural break point — 50 – because that’s the natural age for regular testing.

However, we wanted to take a deeper dive: we used the “age-period-cohort modeling tool” to look at trends by 5-year age groups and trends by year of birth to help disentangle period effects (like changes in medical practice) from cohort effects (behavioral changes seen by generation). We wanted to quantify trends.

Another surprising finding was that rates were also increasing in people in their early 50s despite their annual testing: colon cancer rates increased by 0.5% since the mid-90s and rectal cancer rates increased by 2% annually by mid-90s.

We studied colon and rectal cancer, because most studies look at “colorectal cancer”. While there are similarities, differences are many, particularly with location of tumor in the rectum.

What do these numbers mean for clinical practice?

There’s a long to-do list, but it starts with raising awareness. Young patients are 60% likely to get diagnosed with late-stage disease, mainly because cancer just isn’t on their and their physicians’ radars.

They go months with symptoms like blood in stool and abdominal pain and cramping and are often diagnosed with hemorrhoids. Physicians should be talking to their younger patients about symptoms of colorectal cancer and should conduct follow-ups if they exhibit those symptoms. Physicians should open up dialogue and consider endoscopies and colonoscopies starting at a younger age.

Could genetics, obesity, diet, and/or eating patterns be possible reasons and risk factors behind the risk?

Genetics, not so much. You wouldn’t see genetic changes in the population happening so rapidly. In our study we saw period and cohort effects, which suggest the increased risk is behavioral — body weight and eating patterns play important roles in risk. Since delays in diagnosis are prevalent in young people, physicians should encourage healthier eating and more active lifestyles.

Are increasing colon cancer rates among younger generations only seen in the US?

We only looked at US data, but other studies have been published recently in Canada, Norway, and Australia. These are all high-income countries in which the younger population shares similar behavioral patterns. This is a key finding that can further analyze trends and translate it to clinical practice.

Is a public health campaign needed?

Our type of study was hypothesis generating, but we need cohort studies.

I do think a public health campaign is needed. The problem is that, yes, our study is getting a lot of attention, but while it was at the top of the newsfeed yesterday, it’s now been buried to the bottom. Educational campaigns are crucial to alert clinicians and the general public about this increase in trends and then work to do something about them.