What are the risk factors and preventive measures for colorectal cancer?

Risk Factors for Colorectal Cancer

The most critical modifiable risk factors for colorectal cancer include cigarette smoking, excess body weight, high consumption of alcohol and red/processed meat, low intake of fruits/vegetables/fiber/calcium, and physical inactivity—collectively accounting for over 50% of CRC cases. 1

Non-Modifiable Risk Factors

Age

• Age is the single most important risk factor for colorectal cancer, with incidence rising sharply after age 50 1
• Median age at death from CRC is 68 years 1
• However, incidence in adults under 55 has increased by 51% from 1994-2014, with an 11% increase in mortality from 2005-2015 1

Race and Ethnicity

• Black/African American individuals have the highest incidence and mortality rates of all racial groups 1
• American Indians and Alaska Natives also experience elevated disease burden 1
• African Americans should begin screening at age 45 rather than 50 due to this increased risk 2, 3, 4

Family History and Genetic Factors

• First-degree relative with CRC or advanced adenoma diagnosed before age 60 significantly increases risk 2, 3
• Two or more first-degree relatives with CRC or advanced adenoma at any age elevates risk substantially 1, 5
• Hereditary syndromes including Lynch syndrome (hereditary nonpolyposis colorectal cancer) and familial adenomatous polyposis confer very high risk 1, 2, 5

Personal Medical History

• Previous colorectal cancer or adenomatous polyps places individuals at increased risk requiring surveillance 1, 2
• Inflammatory bowel disease (ulcerative colitis or Crohn's colitis) significantly increases CRC risk, particularly 8 years after onset of pancolitis or 12-15 years after left-sided colitis 1, 5, 6
• Type 2 diabetes is associated with increased CRC risk 1
• History of abdominal or pelvic radiation for previous cancer increases risk 1

Modifiable Lifestyle Risk Factors

Tobacco Use

• Cigarette smoking is a well-established risk factor for developing colorectal cancer 1

Obesity and Physical Inactivity

• Excess body weight significantly increases CRC risk 1
• Physical inactivity independently contributes to CRC development 1

Dietary Factors

• High consumption of red and processed meat increases risk 1
• High alcohol consumption elevates CRC risk 1
• Low intake of fruits and vegetables is associated with increased risk 1
• Low dietary fiber intake contributes to CRC development 1
• Low dietary calcium intake is linked to higher CRC risk 1

Sex

• Male sex is associated with moderately increased risk compared to females 1

Preventive Measures

Lifestyle Modification

• Approximately 50-58% of CRC cases are attributable to modifiable lifestyle factors, representing a substantial opportunity for primary prevention through behavior change 1
• Smoking cessation, maintaining healthy body weight, regular physical activity, and dietary modifications (reducing red/processed meat and alcohol while increasing fruits/vegetables/fiber/calcium) can significantly reduce risk 1

Chemoprevention

• Aspirin use in selected individuals has been demonstrated to reduce CRC likelihood, though patient selection requires careful consideration of bleeding risks 1

Screening as Prevention

• Regular screening beginning at age 45-50 (depending on risk factors) is the most effective secondary prevention strategy, with evidence showing substantial reductions in both CRC incidence and mortality 1, 2, 3, 4
• Screening allows detection and removal of precancerous polyps before they progress to invasive cancer 1

Common Pitfalls

• Failing to identify family history details: Always ask specifically about first-degree relatives, their age at diagnosis, and whether they had CRC or advanced adenomas 1
• Overlooking inflammatory bowel disease duration: The timing of when screening should begin depends on disease duration, not just diagnosis 5, 6
• Not recognizing that younger adults are increasingly affected: The rising incidence in those under 55 means clinicians should maintain vigilance even in younger symptomatic patients 1
• Underestimating the impact of multiple modifiable risk factors: The cumulative effect of lifestyle factors accounts for the majority of CRC cases, making counseling on multiple factors essential 1