Colonoscopy: Screening and Preventing Colorectal Cancer
Colorectal cancer (CRC) is one of the few cancers where prevention is possible through effective screening, particularly colonoscopy. Recent changes in guidelines now recommend starting screening at age 45 due to rising cases in younger individuals, with particular concern for early-onset CRC in South Africa’s diverse population. The effectiveness of colonoscopy relies not only on early detection but also on the specialist’s skill and the use of complete polypectomy rather than biopsy alone. Advances in technology, such as robotic surgery, further enhance outcomes in complex cases, and medical aid schemes are increasingly recognising and funding preventive screening. Choosing a specialised, evidence-based approach offers patients the best protection against CRC.
Colonoscopy: The Science of Prevention
Evidence-Based Screening and the Imperative of Complete Polypectomy
In the landscape of modern oncology, colorectal cancer (CRC) stands apart as a uniquely preventable malignancy. Unlike many cancers where screening serves only to detect the disease at an earlier stage, screening colonoscopy offers the opportunity to interrupt the carcinogenic process in the majority of cases.
However, the efficacy of this prevention is contingent upon two critical variables: the timing of the intervention and the technical quality of the procedure. Current epidemiological data mandates a shift in screening initiation to age 45, while clinical evidence strongly supports complete polypectomy over simple biopsy as the standard of care for premalignant lesions.
The Biological Rationale: The Adenoma-Carcinoma Sequence
The justification for interventional colonoscopy lies in the well-established Adenoma-Carcinoma Sequence. First described by Fearon and Vogelstein, this model delineates the stepwise accumulation of somatic mutations—most commonly initiating with the inactivation of the APC tumor suppressor gene—that drives the transformation of normal colonic epithelium into a benign adenoma, and ultimately, into invasive carcinoma.
This process typically spans a "dwell time" of 5 to 15 years, providing a critical window of opportunity for intervention. By performing a polypectomy during this phase, the endoscopist does not merely detect disease but physically interrupts the biological chain of events required for cancer to develop, effectively preventing the malignancy entirely.
Epidemiology: The Shift to Age 45
Historically, screening guidelines targeted individuals aged 50 and older. However, global cancer registries have identified a significant "birth cohort effect," revealing a sharp increase in the incidence of Early-Onset Colorectal Cancer (EOCRC) in individuals under 50.
The "Young Onset" Phenomenon: Individuals born circa 1990 face double the risk of colon cancer and quadruple the risk of rectal cancer compared to those born in 1950 at the same age.
The South African Context: Local data indicates a distinct racial disparity in age of onset. Studies from KwaZulu-Natal and the Western Cape suggest that Black South African patients often present with CRC a decade earlier than their White counterparts, frequently with more aggressive tumor biology.
Guideline Update: In response to these trends, the American Cancer Society (ACS) and the South African Gastroenterology Society (SAGES) guidelines now advocate for screening to commence at age 45 for all average-risk individuals.
The Statistical Reality: A recent analysis highlighted in the Wall Street Journal confirms that colorectal cancer has now surpassed breast cancer to become the leading cause of cancer death in individuals under 50 in the U.S. While mortality rates have dropped for older adults due to screening, deaths in the under-50 cohort have risen by 1.1% annually since 2005. Most alarmingly, three out of four young patients are diagnosed at an advanced stage, yet only 37% of eligible adults aged 45–49 are up to date with their screening.
Clinical Implication: Waiting until 50 exposes patients to a 5-year window of unmonitored risk during which adenomas can transform into invasive carcinomas
The Specialist Factor: Defining Quality in Endoscopy
Colonoscopy is highly operator-dependent. The protective effect of the procedure correlates directly with the endoscopist’s skill in detecting and removing lesions.
Patients should distinguish between a generalist and a sub-specialist. Dr. Jaco Botes holds the Cert Gastroenterology (SA) qualification. This designation signifies a specialist surgeon or physician who has completed a dedicated fellowship in surgical gastroenterology. In the case of surgeons, training encompasses advanced endoscopic techniques (such as Endoscopic Mucosal Resection) and the surgical management of complex gastrointestinal pathology if it is required, ensuring a comprehensive approach to care.
The Adenoma Detection Rate (ADR)
The Adenoma Detection Rate (ADR) is the primary quality metric in colonoscopy. It represents the proportion of screening colonoscopies in which a pre-cancerous polyp is found.
Evidence: Research published in the New England Journal of Medicine demonstrates that for every 1% increase in a physician's ADR, the patient’s risk of developing interval cancer (cancer that arises between screenings) decreases by 3%.
Variability: Studies comparing specialties consistently show that gastroenterologists achieve significantly higher ADRs and lower "miss rates" compared to non-specialist providers.
Polypectomy vs. Biopsy: The Scientific Argument
A critical failure point in lower-quality screening is the practice of "biopsy and refer"—where a polyp is sampled with forceps but left in situ. This approach is clinically inferior to Complete Polypectomy (immediate removal) due to three biological factors: Sampling Error, Heterogeneity, and Fibrosis.
A. Tumour Heterogeneity and Sampling Error
Colorectal polyps are not biologically uniform. They exhibit intratumoral heterogeneity, meaning different areas of the same polyp may contain different cell lines. A polyp may be predominantly benign adenomatous tissue but harbour a focal area of high-grade dysplasia or invasive carcinoma (cancer).
The Mechanism of Failure: Standard biopsy forceps have a jaw capacity of approximately 2.2mm. When biopsying a lesion >10mm, the sample represents a fraction of the total volume.
False Negatives: If the biopsy is taken from a benign shoulder of the polyp, the pathology report will read "Benign," while the malignant focus remains in the patient. This sampling error provides false reassurance and allows the cancer to progress.
B. The Risk of Fibrosis (The "Non-Lifting" Sign)
Biopsying a polyp induces an inflammatory healing response that leads to submucosal fibrosis (scarring).
Procedural Consequence: Safe endoscopic removal (polypectomy) often requires injecting fluid under the polyp to lift it away from the muscle layer. Scar tissue from a previous biopsy tethers the polyp to the bowel wall, creating a "non-lifting sign."
Surgical Escalation: A polyp that could have been easily removed with a snare during the initial colonoscopy may become unresectable endoscopically after a biopsy. This often necessitates a segmental bowel resection (major abdominal surgery) for a lesion that was originally benign.
C. The Gold Standard: Cold Snare Polypectomy
Evidence supports Cold Snare Polypectomy (CSP) as the superior technique for removing small to medium polyps.
Technique: A wire loop captures the polyp and a margin of normal tissue, mechanically resecting the entire lesion.
Benefit: This ensures R0 resection (complete removal with clear margins), eliminating the risk of sampling error and preventing the development of interval cancers associated with incomplete resection.
Advanced Interventions: Robotic Surgery
While prevention is the goal, complex cases require advanced surgical capability. The Durbanville Colorectal Unit offers the use of the Da Vinci Robotic System for colorectal resections.
Precision: The system provides 3D high-definition visualization and articulated instrumentation, allowing for precise dissection in the narrow pelvis.
Outcomes: This technology is associated with improved preservation of nerves vital for urinary and sexual function, particularly in rectal cancer surgery.
Access and Advocacy
Lead From Behind
We support the global "Lead From Behind" initiative, which leverages high-profile testimonials (such as Ryan Reynolds’ televised colonoscopy) to destigmatize the procedure. Reynolds’ experience highlighted the value of finding and removing an asymptomatic polyp, effectively preventing a future cancer.
Medical Aid Coverage
Recognizing the cost-effectiveness of prevention, Discovery Health and other major medical schemes have updated their benefits. Screening Benefit: Discovery Health covers a screening colonoscopy for members aged 45 to 75. Depending on the medical aid is typically funded from the Screening and Prevention Benefit, rather than the medical savings account, underscoring the shift toward preventative care.
Conclusion
The decision to undergo a screening colonoscopy at age 45 is an evidence-based investment in longevity. However, the procedure is only as effective as the technique employed. By choosing a specialized unit that prioritizes high Adenoma Detection Rates over theatre speed, and adheres to the principles of complete polypectomy, patients effectively eliminate the risk of sampling error and ensure the highest standard of cancer prevention.