Colorectal cancer

• Colorectal cancer is the third most common cancer in the UK.
• Occurrence is strongly associated with a person's age, with almost 75% of cases of colorectal cancer occurring in those people who are aged 65 years or over.
• Risk factors for colorectal cancer are smoking, obesity and lack of physical activity.
• Colorectal cancer is a very treatable cancer. However, the earlier it is diagnosed, then the easier it is to treat. Those people who have their cancer diagnosed at an early stage will usually have a much higher chance of successful treatment compared to those whose cancer has become more widespread.

Colorectal cancer is a common form of malignancy and is a cancer that starts in the colon or the rectum. These cancers can also be called colon cancer or rectal cancer, depending on where they start. Colon cancer and rectal cancer are frequently grouped together, as they have a number of features in common.

Anatomy 

The large intestine consists of the following regions (Figure 1):

• caecum
• ascending colon
• transverse colon
• descending colon
• rectum

Colorectal cancer is divided into different types depending on the type of cell that the cancer started in. When the type of cancer is known, it helps determine the type of treatment.

Adenocarcinomas begin in the gland cells that line the

For most cases of bowel cancer, we do not know what causes it; however, there are some factors that can increase the risk of getting the disease. Some of the risk factors are non–modifiable (these are things where nothing can be done about them, such as age and genetics) (Box 1).

Box 1. Non-modifiable risk factors 

• A family history of colorectal neoplasia: carcinoma; adenoma under the age of 60 years (Weitz et al, 2005)
• A past history of colorectal neoplasm: carcinoma, adenoma
• Inflammatory bowel diseases, for example, ulcerative colitis and Crohn's colitis
• Previous irradiation A history of small bowel cancer, endometrial cancer, breast cancer or ovarian cancer.

There are some risk factors where things can be done about them (modifiable risk factors, such as changes to lifestyle), lowering the person's risk of getting colorectal cancer (Box 2).

Box 2. Some modifiable risk factors associated with colorectal cancer 

• A diet that

The signs and symptoms of colorectal cancer depend on the site of the cancer. In some patients, symptoms do not become obvious until the cancer is far advanced. It is important to note that the development of signs and symptoms may be subtle.

Symptoms of right-side colon cancers:

• weight loss
• anaemia
• faecal occult (i.e. not visible) bleeding
• mass felt in right iliac fossa.

In this instance, disease is more likely to be advanced at presentation.

Symptoms of left-side colon cancers:

• there is often colicky pain
• rectal bleeding (blood in stool)
• bowel obstruction
• tenesmus (continual or recurrent inclination to evacuate the bowels)
• mass felt in left iliac fossa
• early change in bowel habit (diarrhoea, constipation).

Left-side colon cancer disease is more likely to be at a less advanced disease stage at presentation.

The most common presenting symptoms and signs of cancer or large polyps are rectal bleeding, persistent change in bowel

An early diagnosis is essential for effective treatment, providing the greatest chance of survival (von Karsa et al, 2012). Seeking advice early can help to determine onward referral or to rule out the potential of colorectal cancer. See Box 3 for differential diagnoses (the process of differentiating between two or more conditions which share similar signs or symptoms).

Box 3. Differential diagnoses 

• Diverticular disease
• Irritable bowel syndrome
• Inflammatory bowel syndrome
• Haemorrhoids
• Anal cancer.

There are several investigations that are carried out to determine the cause of the patient's symptoms.

A detailed patient history is required, as well as a physical examination (abdominal and rectal). In order to confirm the diagnosis of colorectal cancer, a colonoscopy (see Glossary) is usually offered to patients.

Colonoscopy is the gold standard for making a diagnosis of colorectal cancer. When a colonoscopy is being performed, if a lesion appears suspicious of cancer, then a biopsy is taken and

Treatment options will depend on the patient's unique individual needs. Surgery is the main treatment option for localised colorectal cancer. The use of radiotherapy and chemotherapy may improve survival rates after potentially curative surgery (Scottish Intercollegiate Guidelines Network, 2016).

Surgery may be performed in an attempt to cure or relieve symptoms. There are some types of surgery that will require the formation of a stoma. Various operative procedures can be used, including:

• colectomy (surgical removal of all or part of the colon)
• hemicolectomy (procedure to remove just one side of the colon)
• sigmoid colectomy (surgical removal of the sigmoid colon)
• anterior resection (removal of diseased part of bowel and joining up the healthy sections).

After assessment of needs and working in partnership with the patient, a decision is made to determine if laparoscopic or laparoscopically assisted (keyhole or minimally invasive) surgery might be considered as an alternative to open surgery

The author would like to thank Mrs Frances Cohen for her help and support.