According to the NHS, bowel cancer is one of the most common cancer in the UK. Early-stage colon cancer may be asymptomatic, and some cancers grow slowly, potentially remaining undetected for a significant period. Colon cancer can often develop and progress for several years without causing noticeable symptoms, making it difficult to determine how long someone can live with it unknowingly. Early detection through screening significantly improves the chances of successful treatment and survival.
Although the faecal immunochemical test (testing of faeces) is the optimum screening tests for bowel cancer, blood tests can provide clues about your general health that might lead to further investigations – and are considered by some easier than providing a faecal sample!.
Although blood tests alone cannot diagnose bowel cancer, they can be useful. A standard blood test can reveal low red blood cell counts (anaemia), which can be a sign of rectal bleeding, a possible symptom of bowel cancer. Additionally, blood tests can measure levels of a protein called carcinoembryonic antigen (CEA), which can be elevated in some people with bowel cancer, though again this isn't a definitive diagnosis.
This test measures the different types of cells in your blood. It can show if you have anaemia (too few red blood cells). Some people with colorectal cancer become anaemic because the tumour has been bleeding for a long time.
The liver is central to many body processes. You may also have a blood test to check your liver function, because colorectal cancer can spread to the liver.
Colorectal cancer cells sometimes make substances called tumour markers that can be found in the blood. The most common tumour marker for colorectal cancer is the carcinoembryonic antigen (CEA).
Blood tests for this tumour marker can sometimes suggest someone might have colorectal cancer, but they can’t be used alone to screen for or diagnose cancer. This is because tumour marker levels can sometimes be normal in someone who has cancer and can be abnormal for reasons other than cancer.
Tumour marker tests are used most often along with other tests to monitor patients who have already been diagnosed with colorectal cancer and are receiving treatment. They may help show how well treatment is working or provide an early warning that a cancer has returned.
Treatment for bowel cancer may include
Surgery to physically remove cancer from the bowel.
Chemotherapy, immunotherapy and/or radiotherapy to kill the cancer cells
