UK Screening and Surveillance For Bowel Cancers

Issues of Concern

Epidemiology

Approximately 43,000 people are diagnosed with bowel cancer annually in the UK. The incidence of colorectal cancer increases with age; most patients newly diagnosed with colorectal cancer are aged 60 years or older. Colorectal cancer survival rates vary with age at diagnosis, gender, ethnicity, and socioeconomic status but are most heavily dictated by stage at diagnosis. The 5-year survival rate for the earliest stage (Dukes A) of colorectal cancer is 85%, whereas for the latest stage (Dukes D), it is 10%. Despite the efforts of the NHS, in England, there is a reported 7% to 10% difference in the 1-year relative survival rates for colorectal cancer between the most affluent and deprived populations.[7]

Aetiology

Genetic and environmental factors play a role in the aetiology of colorectal cancer. Understanding the diversity of factors is essential for tailoring effective screening and surveillance strategies for the general and at-risk populations. Approximately 20% of colorectal cancers are linked to genetic risk factors. The risk of an individual developing colorectal cancer doubles in those with a first-degree family history and triples when that family member is younger than 50 years at the time of diagnosis.[8] Hereditary cancer syndromes such as hereditary nonpolyposis cancer syndrome or familial adenomatous polyposis account for 5% to 10% of all colorectal cancer diagnoses.[9] Approximately 1% of all colorectal cancers are due to chronic inflammation due to inflammatory bowel disease.[10]

Environmental factors significantly contribute to the pathogenesis of colorectal cancer. Consuming a diet high in red and processed meats that contain potentially carcinogenic substances has been linked to an increased risk of developing colorectal cancer.[11] Conversely, consuming a diet rich in fruits, vegetables, and fibre appears to offer protective effects against colorectal cancer. Obesity, a chronic inflammatory state characterized by insulin resistance, has also been identified as a risk factor for colorectal cancer; physical inactivity contributes to this risk.[12][13] Individuals with type 2 diabetes are also at an increased risk of colorectal cancer, likely secondary to the same pathogenic mechanisms.[14] Tobacco is a known carcinogen and has adverse effects on colorectal health, as does heavy alcohol consumption.[15][16] 

Pathogenesis

Colorectal cancer can affect the colon and rectum. Rectal cancer accounts for 49.66% of colorectal cancers, colon cancer accounts for 49.09%, and cancers found in both sites account for 1.25%.[17]

The adenoma-carcinoma sequence is a well-documented pathogenic framework for colorectal cancer. Initiated by the development of benign adenomatous polyps within the colonic mucosa, this sequence unfolds through the accumulation of genetic and molecular alterations.[18] These alterations drive the transformation to high-grade dysplastic adenomatous disease. The inactivation of tumour suppressor genes and activation of oncogenes are pivotal to this transformative process.[19] A subset of these dysplastic adenomas will acquire the hallmarks of cancer and become malignant. The adenoma-carcinoma sequence guides early detection efforts and preventive interventions through colonoscopic surveillance and the resection of precursor lesions.[20]

Clinical Significance

Screening Guidelines

Each of the 4 nations in the UK has a slightly different screening programme. Screening is recommended for different age groups within each nation. The recommended age-based screening brackets are:

• England: between 60 and 74 years of age; currently expanding to include individuals between 50 and 59 years of age
• Northern Ireland: between 60 and 74 years of age
• Scotland: between 50 and 74 years of age
• Wales: between 51 and 74 years of age.

Colorectal cancer screening previously employed faecal occult blood tests (FOBT) and shifted to faecal immunochemical tests (FIT) in 2019. FIT utilizes antibodies specific to human haemoglobin (Hb). The results of FIT are not negatively influenced by the presence of nonhuman blood in stools, such as that ingested through diet; this reduces the chance of falsely positive results. The FIT has a sensitivity of 79% and a specificity of 94%, both higher than FOBT.[21][22] Patient uptake rates for FITs are rising; the most recent data reveals 69.6% uptake in England, 62.1% in Northern Ireland, 66.7% in Scotland, and 67.1% in Wales. 

The results of FIT are reported in micrograms of haemoglobin per gram of faeces (µg/g), and the decision threshold is 120 µg/g. Patients whose results fall above this value are referred to a specialist screening practitioner clinic appointment to discuss their results and further investigations, which may include a colonoscopy. Patients with a FIT result below the threshold are offered another FIT in 2 years. 

If a patient presents to their primary care practitioner with symptoms concerning for colorectal cancer, current guidelines recommend performing a FIT. If the result exceeds 10 µg/g, the patient receives an urgent referral into the 2-week wait pathway. If the FIT result does not meet this threshold, but there are ongoing clinical concerns with persistent symptoms, safety net advice is recommended, with further referral as deemed necessary.[23] Colonoscopy is generally performed through the 2-week wait pathway, designed to ensure that patients with symptoms suggestive of colorectal cancer receive a prompt and expedited referral to a specialist within 2 weeks.

Hereditary Colorectal Cancer Guidelines 

Detailed surveillance guidelines exist for average-, moderate-, and high-risk hereditary colorectal cancer surveillance.[3]

• Average-risk patients are those with no family history of colorectal cancer or who do not meet moderate- or high-risk criteria; these patients should adhere to the routine national screening programme.
• Moderate-risk patients are those with one affected first-degree relative diagnosed with colorectal cancer before the age of 50 or 2 affected first-degree relatives diagnosed at any age. Moderate-risk patients should undergo colonoscopy at 55 years of age. If this colonoscopy reveals no abnormalities, the patient may return to the routine national screening programme. If this colonoscopy reveals polyps, the patient should enter the post-polypectomy surveillance guideline programme. 
• High-risk patients are those with a minimum of 3 first-degree relatives with colorectal cancer diagnosed at any age; affected relatives must span a minimum of 2 generations. High-risk patients should undergo colonoscopy every 5 years beginning at 40 years of age. 

Patients suspected of having an underlying genetic disorder, such as familial adenomatous polyposis or hereditary nonpolyposis colon cancer, sometimes referred to as Lynch syndrome, should receive a referral for genetic assessment. Separate in-depth guidelines for these and other genetic disorders exist and are not discussed in this activity.

Surveillance Following Surgical Management With Curative Intent

The National Institute for Health and Care Excellence in the UK (NICE UK) provides recommendations for surveillance following surgical management with curative intent for colorectal cancer. These surveillance recommendations comprise serum carcinoembryonic antigen (CEA) testing every 6 months for 3 years, computed tomography (CT) scans at 1 and 2 years, and colonoscopy at 1 and 3 years. 

Carcinoembryonic antigen: Carcinoembryonic antigen (CEA) is the most commonly used tumour marker in colorectal cancer surveillance. Serum CEA is elevated in as many as 75% of patients with recurrent colorectal cancer, and CEA is often the first indicator of recurrence.[24] However, the sensitivity and specificity of CEA as a marker of recurrence are as low as 44% and 42%, respectively; many benign diseases and most adenocarcinoma subtypes increase serum CEA.[25] Serum CEA is not recommended as a screening or diagnostic test for colorectal cancer. Healthy individuals who do not smoke tobacco typically have a serum CEA of ≤ 3.0 µg/L; tobacco use naturally increases circulating serum CEA, and the upper limit of normal for serum CEA in individuals who smoke is typically 5 µg/L. In patients undergoing surgical intervention for colorectal cancer, elevated serum CEA levels in the pre- or postoperative period are associated with worse outcomes.[26]

Computed tomography: Imaging surveillance regimens vary among NHS trusts. However, CT scans are generally performed at 1-year and 2-year intervals following surgery for colorectal cancer. CT has demonstrated 100% sensitivity and 95.7% specificity in detecting colorectal cancer. CT scans are well-accepted by patients, low-risk, and quick to perform.[27]

Colonoscopy: Guidelines published in 2020 by the British Society of Gastroenterology, Association of Coloproctology of Great Britain and Ireland, and Public Health England delineate pathways for surveillance following polypectomy and resection of colorectal cancer.[28] Per these guidelines, patients diagnosed with colorectal cancer should undergo colonoscopy 1 year following cancer resection.

Patients who have undergone an en-bloc resection of a large, histological R0 nonpedunculated colorectal polyps should undergo a one-time surveillance colonoscopy 3 years following polypectomy. However, patients who have undergone a non–en-bloc excision of a large, histological R0 nonpedunculated colorectal polyp should undergo a site check within 2 to 6 months following polypectomy and another site check at 12 months following polypectomy.

Patients with high-risk colonoscopic findings should undergo another colonoscopy in 3 years. High-risk findings are defined as:

• the presence of 5 or more premalignant polyps
• the presence of 2 or more premalignant colorectal polyps where at least 1 polyp is considered advanced.

Advanced polyps are defined as:

• an adenomatous polyp measuring 10 or more millimetres in size or containing high-grade dysplasia
• a serrated polyp measuring 10 or more millimetres in size or containing any grade of dysplasia.

Other Issues

Contraindications to Screening and Surveillance for Colorectal Cancer

Despite FIT testing being generally risk-free, patients decline screening invitations. Efforts to increase patient uptake and reduce inequalities throughout the UK are ongoing. Individuals have the right to refuse screening or surveillance for any reason. However, screening and surveillance for colorectal cancer may not be advisable in specific circumstances. The circumstances include but are not limited to:

• Patients 75 years or older, for whom the procedural risks or burden may not outweigh the benefits of early detection and intervention.[28]
• Patients of any age with a life expectancy of less than 10 years, for whom the procedural risks or burden may not outweigh the benefits of early detection and intervention.[28] 
• Patients with significant medical comorbidities, such as advanced cardiovascular disease, may be unsuitable candidates for colorectal cancer surveillance. The complication rate for colonoscopy is 4 to 8 for every 10,000 procedures performed and includes bleeding, bowel perforation, pain, and adverse effects of anaesthesia.[29] The incidence of these complications increases significantly in older and medically frail patients, who are also disproportionally affected by the risks of electrolyte disturbance and hypoglycaemia secondary to bowel preparation regimens.[30][31][32]
• Inadequate bowel preparation can be a contraindication to colonoscopic surveillance.
• Patients experiencing postoperative complications following surgical resection of colorectal cancer, such as an anastomotic leak, may be unsuitable for colonoscopic surveillance until their clinical status improves. 

Contraindications for using bowel cleansing agents include the use of lithium, acute intestinal or gastric ulceration, renal impairment, electrolyte imbalances, hypersensitivity to bowel cleansing agents, gastric retention, dysphagia, severe heart failure, reduced consciousness, an acute exacerbation of inflammatory bowel disease, and gastrointestinal obstruction, perforation or ileus.

Alternatives to Colonoscopy

Colonoscopy is considered the gold standard for colorectal cancer screening and surveillance due to its ability to provide direct visualisation of the colon and rectum. However, there are alternate screening and diagnostic methods, each with advantages and limitations. Commonly employed alternatives include sigmoidoscopy, virtual colonoscopy, barium enema, and capsule endoscopy.

Sigmoidoscopy is less invasive than colonoscopy. While sigmoidoscopy may be employed for colorectal screening or surveillance, the procedure examines only the sigmoid colon and rectum; complete visualisation of the colon is not performed.[33]

Virtual colonoscopy, also known as CT colonography, is a radiologic imaging technique that uses CT images to create detailed images of the colon. Virtual colonoscopy is less invasive than traditional colonoscopy and does not require sedation. However, this procedure usually requires bowel preparation, and if abnormalities are detected, a follow-up colonoscopy is typically recommended for biopsy confirmation and treatment.[34]

A barium enema is a radiologic procedure during which the colon is filled with barium contrast material. Barium enemas were historically the preferred screening modality for colorectal cancer but are infrequently performed for this purpose in current clinical practice due to the availability of other, more accurate screening methods.

Capsule endoscopy utilises a small capsule containing a camera that the patient swallows. The camera obtains still images as it passes through the alimentary tract. Capsule endoscopy is primarily used for examining the small intestine and is not a standard colorectal cancer screening or surveillance method.[35]

Enhancing Healthcare Team Outcomes

Multidisciplinary teams enhance colorectal cancer screening and surveillance by promoting collaboration among specialists, ensuring adherence to evidence-based guidelines, and providing personalised patient care. Multidisciplinary teams assess individual risk profiles, recommend appropriate screening strategies, and facilitate early diagnosis of colorectal disease through staging when abnormalities are detected. These teams develop tailored treatment plans, coordinate ongoing care, and address patient needs, including symptom management and psychosocial support. All team members play a vital role in educating patients and promoting informed decision-making, ultimately improving patient outcomes and the overall quality of colorectal cancer management.