Can My Stool be Tested for Bowel Cancer?
RCSEd Communications Team
The Patient Safety Group (PSG) of the Royal College of Surgeons of Edinburgh (RCSEd) are delighted to lend our enthusiastic support to the sixth World Patient Safety Day (WPSD). This event, established by the World Health Organisation (WHO) in 2019, takes place on 17 September every year. It helps to raise global awareness amongst all stakeholders about key Patient Safety issues and foster collaboration between patients, health care workers, health care leaders and policy makers to improve patient safety. Each year a new theme is selected to highlight a priority patient safety area for action.
The theme set by the WHO for this year’s WPSD is “Improving diagnosis for patient safety”, recognising the vital importance of correct and timely diagnosis in ensuring patient safety and improving health outcomes.
Colorectal cancer is the second leading preventable cause of death from cancer (1). If detected early, it can be cured! This is the purpose of cancer screening programs, to identify cancers early or at the premalignant stage (2). Colonoscopy can detect cancer or cancer-forming polyps in their early stages and is the gold standard in detecting colorectal cancer. This is based on the fact that most colorectal cancers develop in preexisting polyps and it takes series of genetic changes over a decade before becoming cancerous lesions (3). It is also an excellent screening modality, and most developed countries recommend screening above 50 years of age. However, it is resource-intensive, has associated risks such as bleeding and perforation, and can be technically challenging to provide to everyone, even in developed countries, let alone on a global scale. The need for training, and a capacity-demand mismatch in most countries, hinders the use of colonoscopy as a screening tool.
But what about our poo? Testing stool for blood is one way to detect colorectal cancer. It started with the guaiac faecal occult blood test (gFOBT), where the stool was tested for blood by applying a chemical that changed colour to detect the presence of iron in the blood if present in the stool. This involved collecting a person's stool and smearing it on test cards for further laboratory testing. The test usually needed to be done three times to increase sensitivity. Additionally, there were food and medication restrictions before these tests, and these tests could also detect blood from sources above the large intestine, which decreases their usefulness as a screening modality for large bowel cancers(4).
Then came the FIT (faecal immunochemical test), which detects human blood using specific antibodies. The FIT needs to be done only once and does not require the food and dietary restrictions associated with gFOBT. The test results provide specific values, allowing us to set cut-off points based on local population data and the desired sensitivity and specificity. It is also more targeted for blood from the large intestine (5).
FIT and gFOBT need to be done at regular intervals if we are screening for colorectal cancer, as bleeding from a tumour is sporadic. But what if we could detect DNA from developing pre-cancerous lesions as well? This is addressed by the faecal DNA test (6). As expected, it is more expensive but has higher sensitivity than the previous two tests. It can detect lesions that could develop into cancer in the future; thus, it needs to be repeated every three years as a screening test.
FIT and faecal DNA tests involve a home kit. The stool can be collected using a small stick provided in the kit and placed into a small solution-filled vial. The kit is designed to make collecting stool for testing less cumbersome and non-repulsive for some as possible.
It is proven that public health cannot be improved through isolated, advanced medical procedures alone but rather through engaging public health measures like education, a healthy lifestyle, early screening, and awareness of its utility. It is the right direction to use advancements in biotechnology to basic screening procedures to provide a test that is accessible, safe, affordable and effective , bringing it closer to an ideal screening test (7). It is also important to appreciate that stool tests should not be cumbersome and messy and rather easy to do which increases adherence to screening programmes. Such tests can ease the burden on colonoscopy lists and provide screening possibilities worldwide, especially for resource-deprived economies. These kits have reached the market as over-the-counter self-detection kits, although their efficacy is doubtful.
All these screening tests are followed by colonoscopy to assess the colon to identify, and remove polyps and to identify cancers.
Our call to action? Colorectal cancer is a preventable disease with a well-recognised premalignant lesion. In the NHS, there is a quality assured bowel cancer screening program that was initially started between the ages of 60-74 with FOBT, which now is replaced with a user-friendly FIT test, and there is also an age extension to 50 years in the next few years (4). This, along with early referral of common bowel symptoms, will ensure the majority of bowel cancers are identified at an early stage, which can be cured with less detrimental effect to quality of life.
Written by:
Prateek Arora . MS, MRCS, DNB , DrNB Surgical Gastro, Senior Clinical Fellow, Colorectal and Peritoneal Oncology Unit, Christie NHS
Co-author: CR Selvasekar MD. FRCSEd (Gen), MFSTEd, MA (Clin Ed), MBA (Health Executive)
Consultant General, Colorectal and Robotic Surgeon, Divisional Medical Director, Clinical Services & Specialist Surgery, The Christie NHS Foundation Trust, Manchester
References
- Siegel RL et al. Cancer statistics, 2024. CA Cancer J Clin. 2024
- Shekleton FE, Okocha M. UK Screening and Surveillance For Bowel Cancers. [Updated 2024 Jan 7].
- Testa U, Pelosi E, Castelli G. Colorectal cancer: genetic abnormalities, tumor progression, tumor heterogeneity, clonal evolution and tumor-initiating cells. Med Sci (Basel). 2018 Apr 13;6(2):31. doi: 10.3390/medsci6020031. PMID: 29652830; PMCID: PMC6024750.
- NCI (national cancer institute)- Colorectal Cancer Screening (PDQ®)–Patient Version 2024
- gov.uk - Bowel cancer screening: programme overview 2024
- Carethers JM. Fecal DNA Testing for Colorectal Cancer Screening. Annu Rev Med. 2020
- Maxim LD, Niebo R, Utell MJ. Screening tests: a review with examples. Inhal Toxicol. 2014 Nov;26(13):811-28
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