- What is Bowel Cancer (Adenocarcinoma of the Caecum)
- Statistics on Bowel Cancer
- Risk Factors for Bowel Cancer
- Progression of Bowel Cancer
- Symptoms of Bowel Cancer
- Clinical Examination of Bowel Cancer
- How is Bowel Cancer diagnosed?
- Prognosis of Bowel Cancer
- How is Bowel Cancer treated?
What is Bowel Cancer (Adenocarcinoma of the Caecum)
Bowel cancer may be of the adenocarcinoma type and usually arise from the epithelium lining the inside of the large bowel which lines the large intestine.
The colon is part of the large bowel. The large bowel (at the caecum) starts at the end of the small bowel (the ileum). The caecum has the appendix running off of it. The start of the colon is the ascending colon. Where this rises to meet the liver (the hepatic flexure) this becomes the transverse colon. The transverse colon goes across the upper abdomen until it becomes adjacent to the spleen (the splenic flexure) and at this point it becomes the descending colon. The large bowel at this point goes down the abdomen to the pelvis at which point it becomes the sigmoid colon (because it curves in an “S” shape, sigma being the Greek for “S”). The sigmoid colon terminates at the rectum, which acts as a storage pouch for faeces before it is evacuated through the anus.
Overall, the function of the large bowel is to absorb water from the stool. When the ilium enters its contents into the caecum, they are extremely liquid and gradually solidify as the contents progress around the large bowel.
Statistics on Bowel Cancer
Bowel cancer is common but occurs very rarely in young adults. It becomes more common as age increases. People in their 50s, 60s and 70s are most at risk, with sex incidence being slightly more common in females.
Geographically, the bowel cancer tumour is found worldwide, but bowel cancer is most common in areas which have low fibre diets (the refined Western diet!). Areas of the world with high fat consumption and low fibre consumption such as Europe, USA and Australia.
Risk Factors for Bowel Cancer
There are a number of factors which increase the risk of developing colon cancers:
Hereditary Conditions of Bowel cancer:
At a particularly high risk are people with hereditary conditions such as Familial Adenomatous Polyposis or Hereditary Non Polyposis Colorectal Cancer. In these conditions it can occur even in young adults, eg. late teens and early 20’s.
Family History of Bowel Cancer:
First degree relatives of patients with colorectal cancer have an increased risk, particularly if the relative develops it at a young age.
Certain types of polyps, notably villous adenomas have a potential to become malignant. Patients who have previously had a polyp in the large bowel should undergo a regular colonoscopy (ask your doctor how often).
Patients who suffer from ulcerative colitis have approximately a ten fold risk of the disease, and should have a colonoscopy carried out regularly.
A high fat, low fibre diet, especially if high in red meat, is the worst diet that predisposes people to this cancer. People who suffer from obesity are also at an increased risk.
Progression of Bowel Cancer
Bowel cancer tumour spreads by invading the bowel wall. Once it crosses through the muscle layer within the bowel wall it gets into the lymphatic vessels, spreading to local and then regional lymph nodes.
Sometimes bowel cancer is spread via the blood stream to the liver, which is the most common area of metastasis from the bowel cancer tumour. Other organs that may be affected by blood borne spread are the lungs, less often the bones, and even less often the brain.
If a lot of tumour cells get through the bowel wall, they tend to float around as a small amount of fluid within the abdomen and can seed the covering of the bowel (peritoneum). This type of seeding produces small nodules throughout the abdomen which irritates tissues and causes the production of large amounts of ascites (fluid).
How is Bowel Cancer diagnosed?
General investigations into bowel cancer may show anaemia or an abnormal liver function test. The blood albumin level may be low. If liver involvement is severe the clotting profile will be abnormal with a raised INR (International Normalized Ratio).
Prognosis of Bowel Cancer
If the bowel cancer has not invaded the muscle wall, it may be cured by surgery. Once the bowel cancer tumour has breached the muscular wall and gone to the regional lymph nodes, about 40% of patients will survive 5 years.
If the bowel cancer tumour has spread to other organs such as the liver or lung, the current 5 year survival is approximately 10%. In general, because cancers of the caecum present later, the prognosis from carcinoma of the caecum is a little worse than other parts of the colon.
How is Bowel Cancer treated?
The bowel cancer treatment of choice is clearly surgery for early bowel cancer disease. For Duke’s Stage A tumours (that have not reached the muscular layer within the bowel wall) this will usually be curative.
If the bowel cancer disease has breached the bowel wall, and especially if it is has gone into the local lymph nodes, adjuvant chemotherapy will increase the chance of cure. The same is true if it has spread to regional lymph nodes.
If the bowel cancer disease has spread further, such as to the liver, longer term palliation can still be achieved by surgery for the primary tumour to prevent bowel obstruction, followed by specific treatment for the metastases.
For liver metastases, a new technique is to place radioactive material into the blood vessels that supply the liver. The radioactive material impacts in the blood vessels supplying the tumour and irradiates the tumour from within. This can be combined with chemotherapy in an attempt to mop up any other bowel cancer tumour cells which have spread elsewhere.
If there is just a solitary liver metastases in one side of the liver, there is quite a strong argument for surgery to remove the single metastasis in bowel cancer patients who are physically otherwise quite well. Following liver resection, chemotherapy would normally be given.
If the bowel cancer disease has spread to bone and is causing pain, local radiotherapy can be very useful at controlling local symptoms. Standard adjuvant therapy is 5-FU and calcium folinate given for six months. Standard therapy for metastatic disease is irinotecan, 5-FU and leucovorin. Each of the agents in this regime is administered by IV injection weekly for 4 weeks every 6 weeks.
Improvement in bowel cancer symptoms is an important measurement. Specific monitoring may be by measurement of serum CEA. If curative surgical resection has been achieved, repeated checks on a yearly basis by colonoscopy are advisable. In metastatic disease, serum CEA can be very helpful in gauging response to bowel cancer treatment. Abnormal liver function tests can be monitored and imaging of any soft tissue metastases such as in the liver or lung can be performed. The bowel cancer symptoms that may require attention are fatigue from anaemia. The bowel cancer patient may require treatment for visceral pain from liver metastases, or less commonly for somatic pain from bone metastases. If lung metastases are present there may be pleural effusions causing breathlessness. Effusions may require drainage.
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