The nuts and bolts bowel cancer screening
By Mr Iain Skinner, Ms Audrey Yeo and Mr Michael Hong
Mr Iain Skinner, Ms Audrey Yeo and Mr Michael Hong are the three specialist Colorectal Surgeons in the broader Wyndham Colorectal Surgery service. All three operate regularly at both St Vincent's Private Hospital Werribee and Fitzroy. All being subspecialty trained in Colorectal surgery they provide an experienced and high quality colorectal surgery and endoscopy service to the Wyndham area with special expertise in the multidisciplinary care of Colorectal Cancer.
The rapid evolution of bowel cancer screening and colonoscopic surveillance guidelines continues to create confusion in primary health care. The National Bowel Cancer Screening Program (NBCSP) has been designed to detect the high risk members of the asymptomatic average risk population between ages 50 and 74.
From 2018 to 2020, every person aged 50 to 74 years of age, in Australia, will be offered bowel cancer screening. Screening will then be offered 2-yearly thereafter. This involves an immunochemical faecal occult blood test (iFOBT) kit. Unlike the previous guaiac-based kits, these more modern kits detect only colonic bleeding and do not require dietary modifications, which will hopefully result in greater compliance.
Colorectal cancers that are detected at an earlier stage have a better outcome. Research has demonstrated that people who are invited to participate in the bowel cancer screening program have a lower risk of death. Similarly, the complete and accurate removal of pre-cancerous colonic polyps reduces colorectal cancer mortality.
A common question that patients ask is 'why not screen with colonoscopy?' The graphic below demonstrates the superiority of screening with iFOBT over colonoscopy. The overall mortality from screening colonoscopy exceeds that from FOBT, due to the inherent risks of colonoscopy. This is in addition to the vast and impractical resources required for a complete population screening colonoscopy program.
Bowel cancer screening is only appropriate for asymptomatic patients. Over 90% of colorectal cancers are found in people over the age of 50 years, which is the rationale for commencing screening at that age. However, patients from 45 years of age can be screened on request. Patients who should proceed directly to Colonoscopic examination include those with symptoms and those at increased risk of colorectal cancer.
- Per rectal bleeding
- Iron deficiency anaemia
- Altered bowel habits
- Abnormal imaging
- Family history (See Table 1).
- Biennial iFOBT should be commenced 10 years prior to colonoscopy screening
- Personal history of adenomatous polyps or cancer - these patients require colonoscopic surveillance
The participation level from the population is simply too low. In 2015-2016, the participation rate was only 41%. Encouragement from general practitioners is the key to improving this poor uptake.
A common question faced by general practitioners is "what is the significance of a positive iFOBT result?" The rate of a positive result is 7%. Only 3.6% of these positive results (0.26% overall) will be found to have cancer. Therefore, the vast majority of patients with a positive result will not have cancer. However, many of these patients will have adenomatous polyps.
The importance of detection and removal of adenomatous polyps, in the prevention of colorectal cancer, cannot be understated. Patients with a positive iFOBT result should be referred to endoscopists who provide a high quality service. High quality endoscopists spend time examining the mucosa carefully to achieve a high rate of adenoma detection. This metric is currently being measured as part of the GESA colonoscopy recertification program.