Understanding the Risk Factors for Colon Cancer

Colon cancer, a type of cancer also known as colorectal cancer (CRC), is one of the most common cancers worldwide. Its incidence is increasing in India, especially among young adults. Understanding the risk factors is essential for preventing and catching the disease early. There are some factors we cannot change, such as age and genetic predisposition, while others are within our control, including diet, lifestyle choices, and medical conditions. This blog post is intended to review the key factors for colon cancer based on clinical research and incidence data for the Indian population, and significant findings for our risk factors for colon cancer.

1. Age and Demographics: The risk increases with age and is most common in patients over 50 years old. However, a recent increase in early-onset CRC among younger adults is concerning. Various lifestyle and environmental patterns likely interact with genetic predisposition. There is new evidence published in India that demonstrates this, particularly considering that younger adults who have an unhealthy diet, are obese, and/or have a family history of cancer, are diagnosed with CRC in greater numbers.

2. Adenomatous polyposis (FAP) accounts for 3 to 5% of colon cancers. Patients with these syndromes typically present with CRC at an earlier age and should be screened at a younger age. Even if you do not have these rare syndromes, having a first-degree relative with colon cancer presents a doubled risk of CRC. The risk increases with multiple family members affected or the presence of polyps. Individuals at increased risk should consider genetic counselling and/or testing.

3. Personal History of Polyps or IBD: Most colorectal cancers (CRCs) are adenomatous polyps. Patients with large polyps, multiple polyps, and/or numerous dysplastic polyps have a significantly increased risk and should be placed under regular check. CRC risk is also increased dramatically by chronic inflammatory bowel diseases (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), especially in the presence of severe or long-standing inflammation (also called indeterminate colitis). Patients with IBD may require colonoscopies earlier and more often.

4. Obesity/ Diabetes/ Physical Activity: Patients who are obese and overweight, and require metabolic management (i.e. diabetes), are also at an increased risk of CRC. Meta-analyses have shown that each 8 kg/m² increase in body mass index (BMI) is associated with approximately a 10% increased risk of CRC, with stronger data observed in studies for men. The link between obesity and CRC has also been demonstrated in Indian studies, comparing the incidence of CRC amongst overweight individuals. Physical activity has been shown to reduce the risk of CRC significantly. A high level of physical activity is associated with a 38% lower risk of CRC in a meta-analysis.

5. The Diet, Red/Processed Meat and Alcohol: Diet can play a significant role in CRC risk. A high diet in red meat and processed meats, especially when high-heat cooked, creates carcinogenic (cancer-causing) properties called heterocyclic amines that can result in DNA damage and increase the risk of cancer. Case-control data in Indian populations show that CRC is more probable for participants who regularly consume red or processed meat and alcohol. A typical range of alcohol consumption (Regular/Moderate) is an increased risk of 20% from those who never or only occasionally drank. Heavy drinkers can be at increased risk of up to 40 to 50%. Sugary foods and ultra-processed foods may also increase the risk of CRC by contributing to insulin resistance and chronic inflammation.

6. Smoking and Environmental Exposures: Tobacco smoking, including second-hand smoking, significantly increases the CRC risk. In Indian studies, current smokers had 3 to 5 times the risk of CRC, especially after 10 years of smoking or heavy smoking. Radiation exposure; chronic exposure during ages 25-35 (with long-term non-medical cigarette smoking), such as abdominal radiation or pelvic radiation from childhood, is also a rare condition which can represent a risk factor. Emerging evidence is also beginning to suggest that toxins from gut microbials such as colibactin-producing E. coli are associated with early-onset CRC in younger patients.

7. Height and Weight in Early Life: Newer studies have shown that a higher BMI in childhood and adolescence is associated with a higher risk of CRC later in life. Each increase of 5 kg/m² in BMI in young adults results in approximately a 12% increase in CRC risk. Each kilogram above normal birth weight is a risk factor for CRC, which relates to a 9% increased risk of CRC. This demonstrates the importance of taking preventive action in early life to reduce the risk of colon cancer ultimately.

8. Protective Factors: Diet, Physical Activity, and Medications: Healthy choices in lifestyle can significantly reduce the risk of colon cancer. Diets that include sources of fibre, whole grains, fruits, vegetables, legumes, magnesium, fish and even coffee or garlic can have protective benefits. Physical activity offers protection against CRC independent of BMI. Low-dose aspirin, calcium supplements, and NSAIDs are other preventive options supported by evidence for patients at average risk; however, these should be considered only under appropriate medical supervision due to potential hazards, such as gastric ulcers.

9. Economic Risk in Younger Adults & Importance of Screening: Though CRC is more common in older adults, the rates in those <50 are dramatically increasing. There are potential contributing factors for rising rates due to obesity, specific diets, sedentary lifestyles, and microbial dysbiosis. Public health guidelines now recommend screening for CRC starting at age 45 in many countries. Home-based stool tests can help increase detection in underrepresented groups.

Prevention Strategies, Public Health Recommendations

The risk for colon cancer can be associated with factors we can change. Thus, the public health strategy in India should include the following:

• A diet higher in fibre, plant-based foods, and healthy fats.
• Decreasing the amounts of red/processed meat, alcohol, sugar and fried foods.
• Encouraging regular physical activity, including at least 150 minutes of moderate-intensity activity each week.
• Supporting weight management/diabetes.
• Providing programs for outreach regarding smoking cessation and reduced alcohol consumption.
• Provide colonoscopy/stool-based screening, including those at risk and individuals who are ageing, who need it (age 45+).
• Provide genetic counselling for families with genetically inherited cancer syndromes. 

Conclusion

The risk of colon cancer is based on immutable factors (e.g., genetic factors, age, ethnicity) and mutable factors (e.g., dietary factors, physical activity, smoking). While the public health approach to colon cancer may differ in India compared to the rest of the world, the lifestyle modifications that have been successful in other countries can also be observed in India.

By leveraging preventive behaviours, screening populations at risk (including access to early detection), and informing patients who may have a family history of risks, healthcare practitioners and public policymakers can reduce the burden of CRC within the Indian healthcare system. Following the identification of informative risk factors and communicating about these factors, the next step is to initiate recommendations to lower the incidence and decrease the morbidity associated with colon cancer in India.