Colorectal Cancer’s Alarming Trend: Understanding the New Age of Risk

Einsley-Marie Janowski, MD, is Associate Professor of Medicine in the Division of Radiation Oncology at the University of Virginia's hospital (UVA Health). Dr. Janowski provides radiation treatment for patients with breast, gastrointestinal, and gynecologic cancers. She is experienced with multiple radiotherapy techniques including intensity modulated radiation therapy (IMRT), volumetric modulated arc therapies (VMAT), stereotactic body radiotherapy (SBRT), Gamma Knife Radiosurgery, intra-operative radiotherapy (IORT), and gynecologic brachytherapy.

Colorectal cancer (CRC) is increasing in frequency, especially among younger populations both in the United States and globally. In the US, CRC is now the top cause of cancer deaths in men and the second leading cause of death in women under the age of 50. While approximately 10% of all new CRCs are early onset at this time, this frequency is increasing each year, with experts estimating that 25% of rectal cancers will be diagnosed in people younger than 50 in the next ten years. Most people diagnosed with early onset CRCs are too young even to have been recommended for routine cancer screenings. These trends have prompted the US Preventative Services Task Force to reduce the recommended age for starting CRC screening to 45, down from the previous recommendation of age 50. Concerningly, these younger patients tend to have more aggressive types of tumors and present to medical attention with more advanced disease. The question many experts are asking is why--what is leading to this increased frequency of CRC in younger patients? Data indicates a complicated process likely related to a variety of factors, including genetic and environmental risk factors. 

Genetic Factors

The most important risk factor for CRC is family history. Having a first-degree relative with CRC can increase the risk of early-onset CRC 2-4 fold. Some common genetic syndromes associated with CRC include familial adenomatous polyposis, which has a nearly 100% risk of developing CRC, and hereditary nonpolyposis, also known as Lynch syndrome, which has a 40-80% risk of developing CRC.

While approximately 30-35% of CRCs can be attributed to hereditary cancer syndromes, up to 65-70% of CRCs are sporadic. Despite what appears to be random CRC development, evidence increasingly indicates that certain patient demographics have a higher risk of CRC development, including male sex, black and Asian ethnicities, and inflammatory bowel disease. The genetic components linked to these non-modifiable factors are complicated. However, it appears that these genetic predispositions can be heavily influenced by other modifiable environmental factors.

Environmental Factors

CRC has been linked to environmental, modifiable risk factors, which include diet, physical inactivity, smoking and alcohol use, and obesity. The common link to many of these modifiable risk factors is the creation of a pro-inflammatory environment in the body in general and in the gut specifically. Specific dietary factors include red and processed meat, high saturated fat and low fiber, high fructose corn syrup, synthetic dyes, and generally processed foods. Some of these dietary factors might have direct carcinogenic effects, while others likely change the composition of the microbiome. Indeed, humans are colonized by residential microbes, which have evolved to help us digest foods and protect us from pathogens in the environment. Microbial composition appears to change over the human life span, with individual organisms and cells in the microbiome competing and cooperating with one another. There is increasing evidence for complex and individual microbial interaction with hosts, with microbial signaling impacting metabolic, neurological, inflammatory, and host-defense functions for local, distant and immunologic interactions. Alterations in the composition of the gut microbiome, also referred to as dysbiosis, have been associated with a growing number of prevalent human diseases, including cancer. Healthy gut microbiomes have been linked to a diverse diet rich in fruits and vegetables.

What Can You Do Now to Minimize Your Risk?

A family history of CRC can call for increased vigilance and early screening. The University of Virginia has geneticists on staff who can help determine what screening tools and frequencies can be appropriate for you. However, in the vast majority of CRCs, these events are sporadic and can be influenced by modifiable risk factors. Evidence indicates that increasing physical activity, shedding excess weight, avoiding smoking and heavy alcohol use, and eating a healthy, balanced, and mostly plant-based diet can decrease the risk of CRC development. Discuss your non-modifiable and modifiable risk factors with your primary care physician to come up with a plan for both appropriate screening and minimizing gut inflammation.

Navigating Warning Signs and Early Detection

Signs of CRC might include rectal bleeding, unexplained anemia, changes in bowel habits, and abdominal pain. Here are the steps to take if you suspect you might have CRC:

• Visit your PCP for evaluation.
• Often, the next steps will include colonoscopies to detect any abnormal growths.
• Treatment of CRC will depend on the tumor's location and stage.

While further research is needed to completely understand the underlying causes of early-onset CRC, early detection can increase the chance of a cure, so don’t wait. Trust your gut to protect your gut!