colorectal cancer

Last edited 10/2022 and last reviewed 06/2023

Colorectal carcinoma is a term used to refer to cancerous growths of the colon, rectum and the appendix (1).

• cancer of the colon is more common when compared to rectal cancer
• in UK around two-thirds (64% in 2009) of all bowel cancers are cancers of the colon and over one-third (36%) are cancers of the rectum (including the anus) (2)
• in a high risk population, the ratio is 2:1 while the rates are similar in countries where the risk is lower
• majority of rectal cancer cases are seen in men while colon cancer cases are divided evenly between men and women (53%)
• occurrence of colorectal cancer is strongly related to age, with almost three-quarters of cases occurring in people aged 65 or over. Colorectal cancer is the second most common cause of cancer death in the UK
• ninety-five percent of malignant colorectal tumours are adenocarcinomas

Majority of colorectal cancers arise from adenomatous polyps most of which are benign but a few may develop into cancer overtime (1).

Colorectal cancer (cancer of the colon or rectum, or bowel cancer) is the fourth most common cancer in the UK, with over 41,000 new cases diagnosed each year according to Cancer Research UK (3).

Most of the tumours are seen in the left side of colon. The percentage distribution of cases within the large bowel in Great Britain between the years 2007-2009 is as follows:

• 22% caecum and ascending colon
• 5% transverse colon
• 3% descending colon
• 20% sigmoid colon
• 7% rectosigmoid junction
• 27% rectum (2)

Much epidemiologic data for these two carcinomas have been grouped, but other aspects of the two diseases differ sufficiently that the two are discussed individually.

Survival rates have improved over time, with almost 60% of people diagnosed with colorectal cancer surviving for at least 5 years (3)

• survival is linked to disease stage at presentation, with better survival the earlier the disease is detected and treated

People with Lynch syndrome have an increased risk of colorectal cancer, with lifetime risk estimated to be between around 50% to 80% (3):

• main strategy to prevent colorectal cancer in people with Lynch syndrome has been regular screening with colonoscopy and polypectomy. Aspirin has been suggested as another potential prevention strategy for colorectal cancer

People who have been treated for colorectal cancer may have long-term side effects of their treatments. For example, low anterior resection syndrome can have major impact on quality of life and daily living, and it affects around 40% of those who have undergone sphincter-preserving surgery for rectal cancer (3).

Association between consumption of ultra-processed foods and risk of colorectal cancer:

• a study found that high consumption of total ultra-processed foods in men and certain subgroups of ultra-processed foods in men and women was associated with an increased risk of colorectal cancer (4):
  • compared with those in the lowest fifth of ultra-processed food consumption, men in the highest fifth of consumption had a 29% higher risk of developing colorectal cancer and the positive association was limited to distal colon cancer (72% increased risk)
    • associations remained significant after further adjustment for body mass index or indicators of nutritional quality of the diet (that is, western dietary pattern or dietary quality score).
    • no association was observed between overall ultra-processed food consumption and risk of colorectal cancer among women
    • among subgroups of ultra-processed foods, higher consumption of meat/poultry/seafood based ready-to-eat products among men and ready-to-eat/heat mixed dishes among women was associated with increased risk of colorectal cancer
    • yogurt and dairy based desserts were negatively associated with the risk of colorectal cancer among women

Reference:

• (1) National Institute for Health and Clinical Excellence (NICE) 2014. Colorectal cancer: the diagnosis and management of colorectal cancer  
• (2) Cancer Research UK 2011. Bowel cancer incidence statistics
• (3) NICE (January 2020). Colorectal cancer.
• (4) Wang L, Du M, Wang K, Khandpur N, Rossato S L, Drouin-Chartier J et al. Association of ultra-processed food consumption with colorectal cancer risk among men and women: results from three prospective US cohort studies BMJ 2022; 378 :e068921 doi:10.1136/bmj-2021-068921