Bowel cancer Flashcards
What is the bowel?
The bowel is part of the digestive system. It is made up of the small bowel (small intestine) and the large bowel (colon and rectum). The small bowel is longer than the large bowel but it gets its name from the fact it is much narrower than the large bowel.
What does the bowel do?
The small bowel breaks down food even further, absorbing the nutrients into the body – undigested waste moves into the colon
The large bowel is made up of the colon and rectum. The body absorbs water from the undigested waste as it moves along the colon towards the rectum. Waste (faeces) is stored in the rectum until it passes out of the body.
What is bowel cancer?
Bowel cancer is a general term for cancer that begins in the large bowel. Depending on where the cancer starts, bowel cancer is sometimes called colon or rectal cancer.
Bowel cancer is one of the most common types of cancer diagnosed in the UK – most people diagnosed with it are over the age of 60.
Stage 1 of bowel cancer
Stage 1 means that the cancer has grown through the inner lining of the bowel, or into the muscle wall, but no further. There is no cancer in the lymph nodes.
Stage 2 of bowel cancer
Stage 2 means the cancer is localised and there is no cancer in the lymph nodes. Stage 2 can be divided into 2A and 2B.
Stage 2A means that the cancer has grown into the outer covering of the bowel.
Stage 2B means that the cancer has grown through the outer covering of the bowel, into the tissues and organs next to it. The cancer has not spread to another area of the body.
Stage 3 of bowel cancer
Stage 3 is divided into 3A, 3B and 3C.
Stage 3A means that the cancer is still in the inner layer of the bowel wall. Or it has grown into the muscle layer. Between 1 to 3 nearby lymph nodes may contain cancer cells.
Stage 3B means that the cancer has grown into the outer lining of the bowel wall. Or into the surrounding body tissues or organs. Between 1 to 3 nearby lymph nodes can contain cancer cells.
Stage 3C means that the cancer can be any size. It has spread to 4 or more nearby lymph nodes. The cancer has not spread to any other part of the body.
Stage 4 of bowel cancer
Stage 4 means that the cancer has spread to other parts of the body. Such as the liver, lungs or bones. The cancer spreads through the lymphatic system or the bloodstream.
What affects survival?
A patient’s outlook depends on the stage of the cancer when it was diagnosed. This means how big it is and whether it has spread.
The type of cancer and grade of the cancer cells can also affect your likely survival. Grade means how abnormal the cells look under the microscope.
The patient’s general health and fitness also affect survival because overall, the fitter they are, the better they may be able to cope with your cancer and treatment.
Some bowel cancers make a protein called carcinoembryonic antigen (CEA). People with high CEA levels before treatment may have a worse outlook.
Bowel cancer can sometimes cause a blockage in the bowel (bowel obstruction). If this happens, patients have a small risk of developing a hole in the wall of the bowel. This is called perforation. People with bowel cancer who have an obstruction or perforation of the bowel have a worse outlook.
What are the signs and symptoms of bowel cancer?
- Bleeding from your bottom or blood in your faeces with no obvious reasons - Changes in your bowel habits such as going more often, diarrhoea or constipation – with no explanation - Losing weight For no reason/without trying - Extreme tiredness With no explanation - Pain or a lump in your stomach
What are risks of bowel cancer you can’t change?
Age
Almost 9 in 10 cases of bowel cancer occur in people aged 60 or over
Family history
1 x first degree relative (mother, father, sibling, child) diagnosed with bowel cancer before the age of 45
2 x first degree relatives diagnosed with bowel cancer at any age
Certain medical conditions
Having severe ulcerative colitis or Crohn’s disease (1 in every 100 cases)
Having Diabetes (although we don’t know why)
History of organ transplant
Gall bladder removed (cholecystectomy)
If you have previously had bowel cancer
If you have had womb, testicular or lymphoma cancer
How does maintaining a healthy BMI reduce the risk of developing bowel cancer?
Excess fat changes the levels of sex hormones, like oestrogen and testosterone, in the body. This may increase the risk of cancer.
The hormone insulin is a very important part of how the body uses energy from food. When people are overweight or obese, there is much more insulin present in the body. It’s not clear how this could lead to cancer, though it could be because insulin affects the levels of growth factors available to cells which tell them to divide.
How does quitting smoking reduce the risk of developing bowel cancer?
The main way that smoking causes cancer is by damaging our DNA, including key genes that protect us against cancer. Many of the chemicals found in cigarettes have been shown to cause DNA damage, including benzene, polonium-210, benzo(a)pyrene and nitrosamines.
This is made worse by other chemicals in cigarettes. For example chromium makes poisons like benzo(a)pyrene stick more strongly to DNA, increasing the chances of serious damage. And chemicals like arsenic and nickel interfere with pathways for repairing damaged DNA. This makes it even more likely that damaged cells will eventually turn cancerous.
Smokers are also less able to handle toxic chemicals than those with healthy lungs and blood. Chemicals in cigarette smoke make it harder for smokers to neutralise or remove toxins, and can make their immune systems less effective too.
It usually takes many years, or decades, for the DNA damage from smoking to cause cancer. Each cigarette can damage DNA in many lung cells, but it is the build up of damage in the same cell that can lead to cancer. However research has shown that for every 15 cigarettes smoked there is a DNA change which could cause a cell to become cancerous. This is why it’s better to give up smoking sooner rather than later.
How does reducing alcohol consumption reduce risk of developing bowel cancer?
In our bodies, alcohol (ethanol) is converted into a toxic chemical called acetaldehyde.
It can cause cancer by damaging DNA and stopping our cells from repairing this damage. The International Agency for Research on Cancer have classified acetaldehyde formed as a result of drinking alcohol as being a cause of cancer, along with alcohol itself.
Acetaldehyde also causes liver cells to grow faster than normal. These regenerating cells are more likely to pick up changes in their genes that could lead to cancer.
Alcohol can cause highly reactive molecules, called Reactive Oxygen Species (ROS), to be produced in our cells. These molecules can damage the DNA, which could cause cancer to develop.
How does maintaining a healthy diet reduce the risk of developing bowel cancer?
Strong evidence shows that eating lots of processed and red meat can increase the risk of bowel cancer, and possibly stomach and pancreatic cancer.
Red meat (including processed red meat) contains a naturally occurring red pigment called haem. Haem could irritate or damage cells in the body or fuel the production of harmful chemicals by bacteria, which could lead to a higher risk of cancer. Almost all red meats contain much greater amounts of haem than white meats.
Chemicals called nitrates and nitrites are often used to preserve processed meat. In the body nitrites can be converted into cancer-causing chemicals called N-nitroso compounds (NOCs). The presence of these chemicals may explain why many studies have found that processed meat increases the risk of cancer more than red meat.
Cooking meat at high temperatures such as grilling or barbecuing can produce cancer-causing chemicals called heterocyclic amines (HCAs) and polycyclic amines (PCAs).
Many studies show that foods high in fibre reduce the risk of bowel cancer. Foods high in fibre include fruits, vegetables, pulses and wholegrain foods, but the strongest evidence is for wholegrains.
Fibre increases the size of faeces, dilutes their contents, and helps people open their bowels (poo) more frequently. This reduces the amount of time harmful chemicals in the faeces stay in contact with the bowel. Fibre may also help gut bacteria produce helpful chemicals that change the conditions in the bowel. All these things could help to reduce the risk of cancer.
How does maintaining a healthy lifestyle reduce risk of bowel cancer?
Physical activity helps food move through our bowels. When food moves through our bowels quickly this reduces the amount of time that the inside lining of the bowel is in contact with any harmful chemicals, like those released when you consume alcohol or red and processed meat. So there’s less chance of them being able to cause damage that could lead to cancer.
Being active also helps control levels of inflammation in the bowel. Inflammation is a normal part of the way our bodies react to injury or infections. But it can sometimes cause even more damage, particularly when it keeps happening in the same place. This can lead to the cells multiplying much more frequently than usual, to replace dead and damaged cells, increasing the chances of mistakes that could lead to cancer.
