Colon cancer takes sides which is important when it comes to diagnosis and treatment of the condition which affects around 268,000 people in the UK. The colon is the large intestine and is around five feet long and in the UK, about 44,100 people get cancer in the colon or rectum each year.
‘Left-sided colon cancer, which occurs further down the intestine and the rectum, in an area called the descending colon and the sigmoid colon, occurs more frequently than right-sided colon cancer but it is are generally easier to detect and treat,’ says Iain Jourdan, a colorectal consultant surgeon based at the Royal Surrey County Hospital.’
‘Right-sided tumours are often more challenging to detect during a colonoscopy because they can be flat and harder to see. This means patients with right-sided colon cancer are more likely to have advanced-stage (stage 3 or 4) cancer when it is detected.
Right sided cancer may also show symptoms later. ‘This is because the contents of the bowl are more liquid on the right side because they have not yet had their moisture content removed. Bowel contents gradually lose their water content and become more solid as they move through the large intestine.
This means it is less likely that an obstruction will occur until tumours are much bigger – and its the obstruction which causes symptoms like pain and bloating which are a tell-tale sign and cause people to seek medical attention,’ says Dr Jourdan.
And left-side tumours have a better prognosis than right-side tumours. ‘Studies show that colon cancer on the left side responds better to chemotherapy and targeted therapies, including HER2 drugs whereas right-side cancer is often more aggressive and less likely to respond to these drugs.’
Some researchers suggest that cancers located in the right compared to the left side of the colon are different and they can be regarded as distinct diseases.
‘While polyps, which are abnormal growths on the bowel lining which can turn cancerous over time, can occur anywhere in the entire colon, they tend to behave differently depending on where they arise.’
Left hand side polyps often grow slowly and may only change gradually into cancerous tumours over several years.’
Right-sided polyps on the other hand are more likely to develop into cancers — which often grow rapidly and have a higher risk for metastasis, spreading to distant body areas.
According to the American Cancer Society, In recent years, research has shown that the genetic mutations found in colon cancer can be different depending on whether it started on the right or left side of the colon. ‘These differences can affect how the cancer responds to certain treatments as well as a person’s prognosis (how well they do after treatment).’ For example, right sided tumours are more likely to have a mutation on the BRAF gene which makes a protein called BRAF which is involved in cell growth. A change to this gene can cause it to make an overactive BRAF protein. This makes cells grow and divide too fast.
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