Colorectal screening

Dr Thobile Goba-Mjwara gives us a rundown on what is needed to implement a colorectal cancer screening programme in SA.

Colorectal cancer (CRC) accounts for about 10% of all malignancies, making it the third most common cancer worldwide. Incidence rates and mortality are, however, increasing in low and middle-income countries while stabilising in high-income countries. In recent years, CRC has been diagnosed at an earlier age with patients presenting with more advanced disease.

The incidence rates of CRC are rapidly increasing in SA. Targeted screening and surveillance programmes for individuals with known colorectal cancer-causing mutations have resulted in increased life expectancy.

SANCAPS

The South African National Cancer Prevention Services (SANCaPS) was established to implement national systems for identifying individuals with inherited cancers, improving their clinical management, and reducing the overall disease burden.

In SA, black patients develop CRC at a younger age than other race groups. It has been postulated that this may have a molecular or genetic basis with a higher propensity towards microsatellite instability (MSI) and hereditary non-polyposis CRC (HNPCC) amongst black patients.

Risk factors

• Family history of CRC
• Obesity
• Hyperlipidaemia
• Physical inactivity
• Diet (increased consumption of red and processed meats and a protective effect with the intake of calcium, fibre, vitamin D, fruit, and vegetables)
• Smoking
• Moderate to heavy alcohol consumption
• Diabetes

The risk conferred by a family history of CRC is dependent on the number of affected relatives and the age of diagnosis of the affected family members (younger ages conferring a higher risk).

Screening modalities

Stool-based tests are reliant on the detection of blood within the gastrointestinal tract (GIT).

Guaiac faecal occult blood tests (gFOBT) detect hidden blood in the stool, whereas faecal immunochemical tests (FIT) detect human globulin.

Blood-based tests, or liquid biopsies, for detecting CRC and precursors, have been shown to increase screening uptake. They offer a non-invasive, safe, acceptable, and convenient mode of screening.

Imaging

Computed tomographic colonography (CTC) allows for the visualisation of premalignant and malignant colorectal lesions through 3D and 4D reconstructions.

Colon capsule (CC) is a variation of small bowel video capsule enteroscopy, utilising a wireless capsule-housed camera to image the large intestine.

Colonoscopy is considered the gold standard for the detection of colorectal neoplasia and CRC. It offers a one-step screening process allowing the detection, diagnosis, and treatment of CRC.

Guidelines for a screening programme

The International Agency for Research on Cancer (IARC) guidelines recommend that 95% of the target population be invited to screening, with a minimum uptake rate of 45% and follow‑up colonoscopy rates of 85%.

Treatment for early-stage disease (Stage 1) is both cheaper and more effective than treating later-stage disease (Stage 2 and beyond).

Training and building capacity for the early diagnosis of CRC and establishing referral pathways and access to the multi-disciplinary management of CRC is an essential start to implementing a screening programme in SA.

The American College of Gastroenterologists (ACG) and the European Society of Gastrointestinal Endoscopy endorse screening with FIT or colonoscopy from the age of 50 in those with an average risk of CRC and younger in those with first-degree relatives (high risk) with CRC.

South Africa

The current practise in SA is an individualised risk-based referral for CRC screening. CTC, MR colonography, and CC are restricted to some tertiary hospitals, academic centres, and private healthcare institutions.

At present, large private healthcare funders cover biennial FIT testing between ages 45–75 years and additionally cover screening by means of colonoscopy.

In all patients with a first‑degree relative with CRC or an advanced adenoma, screening should begin at age 40, or 10 years before the youngest diagnosis in the family, and at an even younger age (35–40) for black patients.

SANCaPS has advocated for the identification of inherited cancers by associating data processing between the National Health Laboratory Service (NHLS), Corporate Data Warehouse (CDW), and the National Cancer Registry.

Furthermore, SANCaPS recommends mandatory testing for mismatch repair genes in all CRC diagnosed <60 years of age to identify genetic MSI tumours.

Dr Thobile Goba-Mjwara is a clinical oncologist at Oncocare Specialist Oncologists in Durban and Hillcrest, KwaZulu-Natal. She completed her specialist training in Radiation Oncology (FC Rad Onc) and Master of Medicine in Radiation Oncology (MMED) in 2021 at Tygerberg Hospital, Stellenbosch University. She has a special interest in breast-, gynaecological-, and prostate cancer.

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