Excess weight may be key driver of early-onset colorectal cancer
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Excess body weight may be a key risk factor for the development of early-onset colorectal cancer, according to research published in International Journal of Cancer.
Prior studies have documented alarming increases in early-onset colorectal cancer since the 1990s.
“Historically, when we’ve thought about early-onset cancer, our belief has been that it is genetic — and in the past, to a large extent, this has been the case,” Wan Yang, PhD, assistant professor of epidemiology at Columbia University’s Mailman School of Public Health, told Healio. “However, over the years, the majority of early-onset cancer cases haven’t had any known family history. So, there must be something happening — either due to environmental exposure or lifestyle factors — that is contributing to this increase in recent years.”
Yang and colleagues used the SEER database to obtain early-onset colorectal cancer incidence data. They used long-term national surveys to obtain data for 11 exposures, including BMI. Investigators aggregated data for individuals aged 30 to 49 years by subgroups defined by time period (range, 1992 to 2016), age, sex and race.
Results showed increases in prevalence of overweight/obesity contributed to an estimated 30% increase in early-onset colorectal cancer among men and an estimated 28% increase among women.
Yang spoke with Healio about the study findings, as well as how large-scale policies and infrastructural improvements may help address the challenge of early-onset colorectal cancer.
Healio: What motivated you to conduct this study?
Yang: The increase we have seen in early-onset colorectal cancer is very concerning. “Early onset” often is defined as being diagnosed before age 50, but a lot of these cases actually are diagnosed before age 40. It’s devastating to get cancer at such a young age. We consider it critical to find out what is causing this increase in the hopes that something can be done to support more effective prevention.
Healio: How did you conduct the study and what did you find?
Yang: Usually, for such epidemiological research, we do a cohort study. We follow a large number of people, measure their exposures and then note how many people have been diagnosed with cancer after a period of time. However, for early-onset cancer, the absolute risk is still fairly low, so we cannot do those traditional studies. To deal with that challenge, we used long-term cancer surveillance data and population exposure surveillance data. We combined those data and used statistical methods to examine 11 different environmental exposures. The top performing model showed excess body weight was the strongest risk factor consistently identified. This was in keeping with several other reports.
We also considered the question of whether — if we were in an alternate reality without much increase in overweight or obesity in the population — there might be a difference in the incidence of early-onset cancer over time. So, we assumed the prevalence of overweight and obesity in the population was maintained at the same level as about 30 years ago, and we put those numbers into our model. It turned out that if we had a much lower level of overweight or obesity in the population, we would not see as much of an increase in early-onset colorectal cancer as we’re seeing. That shows the increase in overweight and obesity in the population, to a very large extent, might explain the increase in early-onset colorectal cancer in recent years.
Healio: What are the potential implications of these findings?
Yang: This confirms other studies that showed excess body weight is associated with increased risk for early-onset colorectal cancer. Also, the counterfactual modeling I mentioned calls attention to the impact of excess body weight on this alarming increase. It also suggests that if we were able to reduce the level of prevalence of overweight and obesity in our population, we might be able to reverse the trend of that increase.
Sometimes, when we think about overweight and obesity, we think about it in terms of individual behavior, so there might be some finger-pointing about individuals not taking proper care of themselves. However, this is based on population data, and it suggests that we need larger-scale policies. It’s not just about individuals — it’s about the health of our entire population. There are a lot of things we can do in terms of policy or improvements to our infrastructure to improve the health of our population as a whole, such as providing people the means to access healthy foods and opportunities for healthy lifestyles like having regular physical activity. This would enable us to improve our population health rather than putting the burden solely on individuals.
Healio: Is there anything else you’d like to mention?
Yang: A few years ago, a guideline update lowered the screening age for colorectal cancer from 50 years to 45 years. However, a lot of people are still not paying as much attention as we would like when they have symptoms. Another concerning situation is that when we looked at the early-onset cancer cases, there is actually a higher percentage of diagnoses at late stages. That suggests delayed detection, and I hope people will pay more attention and seek medical consultation if they do have symptoms.
Reference:
For more information:
Wan Yang, PhD, can be reached at Columbia University Mailman School of Public Health, 722 W. 168th St., New York, NY 10032; email: wy2202@cumc.columbia.edu.
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