Colorectal cancer is the third most common cancer and the second leading cause of cancer death in the United States. It is estimated that in 2020 there will be 148,000 new cases of colorectal cancer with 53,000 people dying of the disease. Since the early 1990’s there has been a rather dramatic decrease in the incidence (frequency) of colorectal cancer in the population older than 50 years. At the same time there has been a dramatic increase in the incidence (frequency) of colorectal cancer in persons less than 50 years, with the largest increase in the 40-49 year old age group. That being said, colorectal cancer is still predominately a cancer of adults over age 50 with the average age at diagnosis being 67 years. Currently about 1 in 9 colorectal cancer diagnoses is in persons less than 50.
Between 2008 and 2017 the death rate from colorectal cancer has declined by 2.6% per year for adults over age 55 but has increased by 1% per year for adults younger than age 55. This may be due to a delay in diagnosis in younger people, younger people being diagnosed with more advanced cancers and colorectal cancers diagnosed at a younger age tend to be more aggressive.
Most colorectal cancer diagnosed in adults less than 50 are what are called sporadic, meaning they do not have a genetic or family risk and they are not associated with a pre-existing disease such as inflammatory bowel disease.
The reasons for the increase in colorectal cancers in young adults are poorly understood. Increases in the incidence have occurred more rapidly than can be accounted for by changes in genetics. It is estimated that more than half (55%) of colorectal cancers are attributable to modifiable lifestyle risk factors and these may very well play a role in the increasing incidence in young adults. Modifiable lifestyle factors that increase the risk of colorectal cancer include excess body weight, physical inactivity, long term smoking, heavy alcohol consumption, type 2 diabetes, low calcium intake, high consumption of processed meats and low consumption of fiber containing foods such as nuts, seeds, vegetables and fruits. Also research is beginning to focus on the composition of the gut microbiome (those trillions of bacteria in your gut) and how changes to the microbiome through poor diet, overuse of antibiotics, stress and obesity may influence the risk for colorectal cancer.
Because colorectal cancer is perceived as a disease affecting only older adults it is imperative that younger adults understand the potential signs and symptoms of colorectal cancer. Symptoms include rectal bleeding, blood in the stool, change in bowel habits or stool shape (stools becoming narrower), the feeling that the bowel is not completely empty, abdominal cramping or pain, decreased appetite or weight loss. In some cases blood loss over time will result in symptoms of weakness and fatigue. Given the increase in incidence of colorectal cancer in young adults timely evaluation of persistent symptoms is important.
When to begin screening for colorectal cancer is controversial. The current recommendation is to begin screening (looking for a cancer or precursor to cancer called a polyp before a person has symptoms) at age 50 with colonoscopy being the gold standard. The American Cancer Society recommends colorectal screening starting at age 45 because of the rising incidence of colorectal cancer in adults under age 50. This recommendation has not been widely adopted and is usually not paid for by insurance.
Not only has there been an increase in colorectal cancer in young adults (age less than 50) but there has been a significant increase in cancers of the uterus, pancreas, kidney, gallbladder and multiple myeloma in younger adults and this risk rises more in successively younger generations.
The bottom line is that younger and younger adults are being diagnosed with colorectal cancer and up to half may be lifestyle associated.
1) Stoffel, EM, Murphy, CC, Epidemiology and Mechanisms of the Increasing Incidence of Colon and Rectal Cancers in Young Adults. Gastroenterology. 2020;158:341-353.
2) Siegel, RL, et al, Colorectal Cancer Incidence Patterns in the United States, 1974-2013. J Natl Cancer Inst. 2017;109(8):1-6.
4) Venugopal, AV, Stoffel, EM. Colorectal Cancer in Young Adults. Curr Treat Options Gastro.2019;17:89-98.