Colorectal Cancer

Definition/diagnostic criteria

Colorectal cancer (CRC) refers to carcinoma that occurs in the colon or rectum. The condition is characterised histopathologically, with the majority being adenocarcinomas. Diagnosis is confirmed through colonoscopic biopsy and histological examination of tissue samples.

Epidemiology

CRC is the fourth most common cancer in the UK, with significant morbidity and mortality. It predominantly affects older adults, with a higher incidence in those aged 60 and above. Risk factors include family history, genetic predispositions (eg, Lynch syndrome), lifestyle factors (diet, physical inactivity, obesity), smoking, and alcohol consumption. The incidence of CRC in the UK highlights the need for effective screening programmes, currently recommended via the NHS Bowel Cancer Screening Programme for individuals aged 60-74.

Diagnosis

Clinical features

Symptoms of CRC may include changes in bowel habit (persistent diarrhoea or constipation), rectal bleeding or blood in the stool, abdominal pain, unexplained weight loss, and fatigue. Importantly, early-stage CRC may be asymptomatic, underlining the importance of screening and early detection strategies.

Investigations

Diagnosis involves a combination of clinical evaluation and investigations:

• Fecal Immunochemical Test (FIT): Used in screening and symptomatic patients to detect occult blood in stool. It is currently used to help stratify urgency of secondary care assessment in symptomatic patients.
• Colonoscopy: Gold standard for CRC diagnosis, allowing for visual examination of the colon and rectum and biopsy of suspicious lesions.
• Computed Tomography (CT) Colonography: An alternative for patients unable to undergo colonoscopy.
• Blood Tests: Including full blood count (for anaemia detection) and liver function tests to evaluate for metastatic disease.

Typical abnormalities found in investigations include irregular mass lesions or polyps on imaging, and histopathological confirmation of adenocarcinoma in biopsies.

Treatment

Treatment depends on the stage of the disease, patient’s overall health, and preferences. Options include:

• Surgical Resection: The primary treatment for localized CRC, aiming for complete removal of the tumor and affected lymph nodes.
• Chemotherapy and Radiotherapy: Used as adjuvant treatments post-surgery in advanced cases or neoadjuvantly to downstage tumours preoperatively.
• Targeted Therapies: For metastatic CRC, including monoclonal antibodies and kinase inhibitors, based on specific genetic mutations in the tumour.

Prognosis

The prognosis of CRC varies significantly with the stage at diagnosis. Early-stage disease has a 5-year survival rate of over 90%, which decreases to approximately 10% for metastatic disease. Factors influencing prognosis include tumour stage, molecular characteristics, patient age, and comorbidities. Regular follow-up and surveillance post-treatment are crucial for detecting recurrence.