The problem of surviving bowel cancer
Bowel cancer (also called colorectal cancer) is the fourth most common type of cancer in the UK and can be especially deadly if diagnosed at a late stage. Tumour staging assesses the severity of the cancer and higher stages are known to reduce the chances of survival . UK national statistics show that over nine out of every 10 people diagnosed are alive five years after diagnosis at the earliest stage (Stage I), where the cancer is confined to the bowel lining. This drops to only one in every 10 people if diagnosed at a late stage (Stage IV), where the cancer has spread to other organs . With over half of the patients diagnosed with bowel cancer in the UK being diagnosed at a late stage, bowel cancer has become the second most common type of cancer that kills. There is a need for earlier detection of bowel cancer.
Can the full blood count test help?
A full blood count is a common type of blood test and may play a part in early detection of bowel cancer. The test involves measuring up to 20 individual components from the blood sample taken from a patient. One component measured is haemoglobin, which carries oxygen around the body and may lower due to rectal bleeding, which is a known symptom of bowel cancer. Another is platelets, which help stop bleeding .
What we did
We are a team of researchers led by Pradeep Virdee and based in NDORMS, a medical department in the University of Oxford. Our goal was to give a complete picture of what we know about this test’s ability to identify people with this cancer. We therefore did a systematic review, which brings together many research papers for projects previously completed by other researchers, of which we identified 53 projects. This includes looking to see if the blood test results were different between healthy people and patients who were diagnosed with bowel cancer. If there were differences present, we also checked to see how early on these differences could be seen to understand the time frame in which they occur and to see if they can help detect bowel cancer at early stages.
What we found
After comparing the findings from the 53 previous research projects identified, we found that six of the 20 full blood count components were related to the presence of bowel cancer. We found that patients with bowel cancer had lower levels of three components (red blood cells, haemoglobin, and mean corpuscular volume), and higher levels of another three components (red blood cell distribution width, white blood cell count, and platelets) compared to those who had not been diagnosed with bowel cancer. The remaining 14 components either showed no difference between those who did and did not have bowel cancer or were not assessed by enough studies for us to make any conclusions about them .
Longer lines represent a larger difference from a healthy person
These differences were largest when the full blood count blood test was performed less than six months before the diagnosis being made. Many of the previous research projects also found smaller differences that appeared much earlier, more than three years before a diagnosis was made, a time where the tumour may be at an early stage. However, these differences are so small that they would not be obvious to a doctor or nurse reading the full blood count blood test results.
How these results will make a difference in the future
We are currently developing a decision aid that will help doctors see how likely a patient is to have bowel cancer. This decision aid will be an electronic tool based on the differences in blood test results that occur early on to help earlier detection of bowel cancer.
This work was funded by the National Institute for Health Research, Doctoral Research Fellowship programme (DRF-2018-11-ST2-057). This report presents independent research and the views expressed are those of the authors and not necessarily those of the NIHR, NHS, or Department of Health and Social Care.
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11 November 2020
Part of an occasional series of articles where University of Oxford researchers from our department look at recently published research in their field.