Colorectal Cancer Prevention: Getting Back on Track

29 May is World Digestive Health Day and this year’s campaign by the World Gastroenterology Organisation (WGO) centres on colorectal cancer. Entitled ‘Colorectal Cancer Prevention: Getting Back on Track’, the campaign aims to improve the diagnosis and management of colorectal cancer [1]. Given Porterhouse Medical’s long heritage in oncology, we are proud to add our voice to the campaign and share our knowledge.

The pathophysiology of colorectal cancer

Most colorectal cancers start as a growth on the inner lining of the colon or rectum. These growths are known as polyps and can develop into cancer over time, which might take many years. [2]

There are three main types of polyps, which are associated with different risks for cancer [3,4]:

Adenomatous polyps (adenomas) are categorised as tubular, villous and tubulovillous according to their growth patterns. Adenomas are classified as a precancerous condition, as they sometimes become cancerous, and thus termed adenocarcinomas.
Hyperplastic polyps and inflammatory polyps are more common than adenomas and are typically not considered to be precancerous. If a patient has a polyp of this type that is large (more than 1 cm), a colonoscopy may be required.
Sessile serrated polyps and traditional serrated adenomas have a sawtooth pattern on their surface; these polyps have a high risk of cancer, so they are typically treated like adenomas.

There are other factors that can increase a person’s risk of developing colorectal cancer. This can include finding a polyp greater than 1 cm, finding more than three polyps, or having abnormal cells remaining after polyp removal [5].

If a polyp transforms to become cancerous, the tumour can grow into the walls of the colon or rectum. Colorectal cancer starts in the mucosal layer that lines the gut and can grow outward through some or all of the layers. Once in the wall, the cancer can grow into blood vessels or lymphatic vessels, enabling the cancer cells to travel to other nearby lymph nodes or distant parts of the body in a process termed metastasis. [2]

Types of cancer in the colon and rectum

Most colorectal cancers are adenocarcinomas, which grow in the glandular cells of the body and commonly occur in breast, lung, pancreatic and prostate cancer [2, 6]. Adenocarcinomas can occur in varying subtypes. Three major types are common for colorectal cancer: classical adenocarcinoma, signet ring carcinoma (SRCC) and mucinous adenocarcinoma [7]. SRCC is a rare form of highly malignant adenocarcinoma comprising 0.5%–2.6% of all adenocarcinomas [8]. Mucinous adenocarcinoma is characterised by high quantities of extracellular mucus that accounts for 50% of the tumour volume [9]. Some researchers believe that the mucus can cause the cancer cells to spread more quickly throughout the body and become more aggressive than typical adenocarcinomas [10]. Although these two subtypes of adenocarcinoma occur less frequently than classical adenocarcinoma, they are associated with a poor prognosis for the patient [5].

Less common tumours that start in the colon and rectum include [10]:

Primary colorectal lymphomas, which originate in immune cells.
Gastrointestinal stromal tumours, which start in interstitial cells of Cajal found in the circular muscle of the colon. These can be benign and can be found anywhere in the digestive tract and are not commonly present in the colon.
Leiomyosarcoma, a rare type of cancer that grows in smooth muscles, which therefore affects the hollow organs of the body, including organs in the digestive system.
Carcinoid tumours, which originate in neuroendocrine cells in the intestine.

Causes of colorectal cancer

Colorectal cancer encompasses a range of cancers that affect the bowels. There is no singular cause of these cancers, but there are factors that can increase the likelihood of developing this disease, which are illustrated in the table below.

Table 1. Factors that can increase the likelihood of developing colorectal cancer [11, 12]

	Age	Ageing is a risk factor for bowel cancer. More than 9 in 10 cases of colorectal cancer develop in adults over the age of 50 years.
	Family history	Having a first-degree relative with colorectal cancer (i.e. parents or siblings) under the age of 50 years can increase the lifetime risk of developing colorectal cancer by 230% [13].
	Diet	Consuming a diet that is rich in red meat and processed meat (over 90 g a day) has been linked to a higher likelihood of developing colorectal cancer. It is recommended that people cut their meat consumption down to 70 g a day or less. A low-fibre diet has also been linked to the development of bowel cancer.
	Smoking	Smoking is a strong causal factor for developing cancer because of DNA damage induced by toxins in cigarette smoke.
	Alcohol	Consuming alcohol regularly in quantities that exceed recommended limits can damage cells, prevent cell repair and increase cell division, which increases the risk of cancer.
	Inactivity and obesity	Being inactive or obese can lead to insulin resistance through the development of type 2 diabetes, which has been linked to stimulation of colon cancer cells.
	Digestive disorders	Having a pre-existing digestive disorder, such as Crohn’s disease or ulcerative colitis, increases the likelihood of colorectal cancer because of the presence of inflammation and increased cell turnover.
	Genetic conditions	Inheriting gene mutations can increase the chance of developing colorectal cancer.

Symptoms of colorectal cancer

People with colorectal cancer may experience a variety of different symptoms or signs. Some of these may be common to other conditions such as Crohn’s disease or irritable bowel syndrome.

Symptoms and signs include [14]:

Diarrhoea, constipation or feeling that the bowel has not been emptied
Stools that are thinner or narrower than usual
Blood when wiping after a bowel movement
Stools that have dark red or bright red blood in them
Unintentional weight loss
Abdominal pain or discomfort, including gas pains, bloating, cramps and feeling very full
Fatigue
Unexplained iron deficiency anaemia

Screening for colorectal cancer

In the UK, everyone aged 55 years and over is offered a faecal immunochemical test which tests whether blood is present in the stool [15]. If the sample tests positive, a colonoscopy is typically performed shortly afterwards to attempt to find evidence of colorectal cancer [15]. A biopsy can also be taken to test a small amount of tissue to make a diagnosis of colorectal cancer [16].

Additional tests might be performed to identify specific genes, proteins and other factors that are unique to the tumour. This can inform a clinician of whether immunotherapy should be used in patients with metastatic disease. [16]

Treatment and getting back on track

There are many options for treatment once a diagnosis has been made.

Surgery is the most common treatment for bowel cancer and aims to remove the cancerous tissue. For colon cancer, this can range from just a local excision of a small piece of the lining of the colon if the cancer is identified early, to a colectomy whereby an entire section of the colon is removed if the cancer has spread into the surrounding muscles [17]. For rectal cancer, if a local resection is not sufficient, a total mesorectal excision would be required, which reduces the risk of the cancer returning through the removal of all the lymph nodes [18].

Chemotherapy is another option to treat colorectal cancer and is often used after surgery to remove any remaining cancerous cells that could not be excised. It may also be given before surgery with the aim of shrinking the tumour to reduce the need for invasive surgery. [19]

Colorectal cancer can also be treated with radiotherapy, but this is less common that other treatments mentioned above. Radiotherapy can be used prior to surgery, or in early-stage cancers instead of surgery. It can also be used palliatively to control symptoms and slow the spread of cancer. Radiotherapy can be administered externally or internally (brachytherapy) using a tube inserted into the rectum to direct the high-energy waves to the cancerous growth. [20]

If diagnosed early, colorectal cancer is highly treatable and has a good prognosis [21]. Participation in screening programmes is essential to identify early-stage disease and improve the outlook for patients.

Living with the aftermath of surgery, radiotherapy or chemotherapy can be daunting, so it is important for patients and survivors to seek support from their medical team. For more information on colorectal cancer, visit Bowel Cancer UK.

The information in this article is not intended or implied to be a substitute for professional medical advice, diagnosis or treatment. All content is for general information purposes only. Always seek the guidance of your doctor or other qualified healthcare professional with any questions you may have regarding your health or medical condition.

References

World Gastroenterology Organisation. World Digestive Health Day 2022. Available at: http://wdhd.worldgastroenterology.org/. Accessed May 2022.
American Cancer Society. What is Colorectal Cancer? Available at: https://www.cancer.org/cancer/colon-rectal-cancer/about/what-is-colorectal-cancer.html. Accessed May 2022.
Colorectal Cancer. Available at: https://www.webmd.com/colorectal-cancer/colorectal-polyps-cancer. Accessed May 2022.
American Cancer Society. Understanding Your Pathology Report: Colon Polyps (Sessile or Traditional Serrated Adenomas). Retrieved from American Cancer Society: https://www.cancer.org/treatment/understanding-your-diagnosis/tests/understanding-your-pathology-report/colon-pathology/colon-polyps-sessile-or-traditional-serrated-adenomas.html. Accessed May 2022.
American Cancer Society. What is Colorectal Cancer? Available at: https://www.cancer.org/cancer/colon-rectal-cancer/about/what-is-colorectal-cancer.html. Accessed May 2022.
Adenocarcinoma. Available at: https://www.webmd.com/cancer/what-is-adenocarcinoma. Accessed May 2022.
Sheng H, Wei X, Mao M et al. Adenocarcinoma with mixed subtypes is a rare but aggressive histologic subtype in colorectal cancer. BMC Cancer (2019); 19 (1071).
Bademci R, Bollo J, Martinez, M. C et al. Colorectal cancer prognosis: The impact of signet ring cell. Gastrointestinal Tumors (2019); 6 (3-4): 57-63.
Luo C, Cen S, Ding, G et al. Mucinous colorectal adenocarcinoma: clinical pathology and treatment options. Cancer Communications (2019); 39 (13).
Cancer Treatment Centers of America. Colorectal cancer types. Available at: https://www.cancercenter.com/cancer-types/colorectal-cancer/types. Accessed May 2022.
Bowel Cancer – Causes. Available at: https://www.nhs.uk/conditions/bowel-cancer/causes/. Accessed May 2022.
Centers for Disease Control and Prevention. What Are the Risk Factors for Colorectal Cancer? Available at: https://www.cdc.gov/cancer/colorectal/basic_info/risk_factors.htm. Accessed May 2022.
Taylor DP, Stoddard GJ, Burt R, et al. How well does family history predict who will get colorectal cancer? Implications for cancer screening and counselling. Genetics in Medicine (2011); 13: 385-391.
Mayo Clinic. Colon Cancer. Available at: https://www.mayoclinic.org/diseases-conditions/colon-cancer/symptoms-causes/syc-20353669. Accessed May 2022.
Bowel Cancer Screening. Available at: https://www.nhs.uk/conditions/bowel-cancer-screening/. Accessed May 2022.
Net. Colorectal Cancer: Diagnosis. Available at: https://www.cancer.net/cancer-types/colorectal-cancer/diagnosis. Accessed May 2022.
Cancer Research UK. Surgery for colon cancer. Available at: https://www.cancerresearchuk.org/about-cancer/bowel-cancer/treatment/treatment-colon/surgery-colon. Accessed May 2022.
Macmillan Cancer Support. Types of surgery for rectal cancer. Available at: https://www.macmillan.org.uk/cancer-information-and-support/treatments-and-drugs/types-of-surgery-for-rectal-cancer#:~:text=Total%20mesorectal%20excision%20(TME),-Most%20people%20with&text=A%20TME%20is%20when%20the,of%20the%20cancer%20coming%20back. Accessed May 2022.
American Cancer Society. Chemotherapy for colorectal cancer. Available at: https://www.cancer.org/cancer/colon-rectal-cancer/treating/chemotherapy.html. Accessed May 2022.
American Cancer Society. Radiation therapy for colorectal cancer. Available at: https://www.cancer.org/cancer/colon-rectal-cancer/treating/radiation-therapy.html. Accessed May 2022.
Bowel Cancer – Treatment. Available at: https://www.nhs.uk/conditions/bowel-cancer/treatment/. Accessed May 2022.

Author: Vicky Hill. PhD Placement Student. Porterhouse Medical