colorectal cancer (bowel cancer)

see also:

• neoplasia / cancer / tumours
• Low-grade appendiceal mucinous neoplasm (LAMN)
• http://info.cancerresearchuk.org/cancerstats/types/bowel/index.htm

• see http://www.cancerresearchuk.org/cancer-info/cancerstats/types/bowel/riskfactors/
• Australians born after 1990 have twice the risk of colon cancer than those born in 1950, and 4x the risk of rectal cancer - similar trends in many other countries - but the cause of this is not clear although may be related to more sedentary lifestyle or diet changes ¹⁾
• chronic inflammation:
  • inflammatory bowel disease (IBD)
    • 70% increased risk
    • > 20 years of disease gives 5% risk of developing cancer
• genetics:
  • familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC)
    • account for 5% of colorectal cancers
    • almost all FAP patients develop bowel cancer by age 40
    • 9 in 10 males and 7 in 10 females with HNPCC develop bowel cancer by age 70
  • other genetic syndromes:
    • account for 20% of colorectal cancers
    • first-degree relative with colorectal cancer ⇒ 2x risk colorectal cancer and 70% higher risk of adenoma
    • BRCA1 mutations may account for some of this excess familial risk, particularly in younger women
    • 3 gene alleles appear to have increased risk of 1.18 per allele per quartile of average processed meat intake ²⁾
    • tall people:
      • it appears that for every 5cm increase in height, colon cancer risk is 11% higher in females and 9% higher in males, and rectum/anus cancer risk is 9% higher in females and 6% higher in males
• diet:
  • processed meat (see above)
  • red meat:
    • 17-30% increased risk if eat 100-120g/day red meat
  • low fibre diet:
    • risk appears to be reduced by 10% for every 10g/day total dietary fibre and cereal fibre
  • possible risk factors:
    • eggs:
      • risk may be 29% higher in people with the highest egg consumption, compared with those with the lowest
    • low non-starch vegetable/fruit diet:
      • risk appears to be 2% lower per 100g/day of vegetables consumed
      • risk appears to be 11% lower in those with the highest intake of fruits compared with those with the lowest intake
    • low milk diet or low calcium diet:
      • risk appears to be 9-15% lower per 200-250g/day of milk consumed
      • however, calcium and Vit D supplements effect on risk is unclear
    • low folate diet:
      • 31% reduction in bowel cancer risk for people with the highest overall folate intake 12-16 years before diagnosis, but no effect of intakes in the more recent past
• obesity
  • risk appears to be 33% higher in people who are obese by BMI compared to normal BMI
  • risk of colorectal adenoma is 47% higher in people who are obese by BMI
• diabetes mellitus
  • type II diabetes have 22-30% increased risk of bowel cancer, compared with non-diabetics
  • metformin is associated with an 11-36% decrease in bowel cancer risk
  • insulin is associated with a 37-61% increased risk
• sedentary
  • the most physically active people have 14-30% lower risk of colon cancer, compared with those least physically active
• alcohol
  • risk is 21% higher in people who drink 1.6-6.2 alcohol units per day, compared with non-/occasional drinkers
  • risk is 52% higher in those who consume 6.2 units or more per day, compared with non-/occasional drinkers
  • risk increases by 7% per unit of alcohol consumed per day
  • a 2026 study suggests current drinkers with an average lifetime alcohol intake of ≥14 drinks per week (heavy drinkers) had a 25% higher risk of developing colorectal cancer and a 95% higher risk of developing rectal cancer compared with those with an average lifetime alcohol intake of <1 drink per week (light drinkers) - heavy drinking throughout adulthood was linked to a 91% higher risk of colorectal cancer compared with consistent light drinking³⁾
• smoking
  • risk is 20-21% higher in current cigarette smokers compared with never-smokers
  • risk is 17-25% higher in former cigarette smokers compared with never smokers
  • risk increases with the number of cigarettes smoked per day, by 7-11% per 10 cigarettes per day
• human papilloma virus (HPV)
  • 10x risk of colorectal cancer
  • 90% of anal cancers are linked to HPV infection
• Helicobacter
  • H.pylori infection increases risk by 39%
• radiation
  • accounts for 1% of colorectal cancers in Western society
• oral flora
  • in a 2024 study, a specific subtype of Fusobacterium nucleatum has been found in 50% of colorectal tumours and is thought to hasten disease progression