What causes bowel cancer to spread?
If the cancer in the bowel is not detected and removed at an early stage, part of the tumour can break off from the main bowel tumour and spread, usually via the lymphatic system or bloodstream, to nearby lymph nodes or other parts of the body.
Your cancer may be advanced when it is first diagnosed. Or it may come back some time after you are first treated.
If the cancer has broken through the wall of the bowel and cancer cells have spread into surrounding tissues in the abdomen and pelvis, this is known as local spread.
Secondary spread (metastasis)
If the cancer has spread to another part of the body (for example, the liver or lungs) is it called secondary cancer or metastatic cancer.
The liver is second only to the lymph nodes as the most common part of the body for bowel cancer cells to spread to. The liver is a common site for bowel cancer cells to spread to as the liver receives most of its blood supply from the portal vein (the vein that carries blood from the intestines and spleen to the liver).
If your bowel cancer has spread in this way, you have secondary bowel cancer in your liver – not liver cancer. Your treatment is dependent on where the cancer started and therefore the treatment you have must work on bowel cancer and not liver cancer cells.
The next most common part of the body for bowel cancer cells to spread to is the lungs.
Once a bowel cancer has spread to another part of the body, it is unlikely to be curable. If your cancer is advanced when it is first diagnosed you may be offered chemotherapy to keep it under control. You may have just one drug or a combination of drugs.
Some people with bowel cancer that has spread receive a monoclonal antibody, a type of biological therapy and are a different type of treatment to chemotherapy. Ask your oncologist about the choices available to you, and the combination option.
In some circumstances you may have surgery.
The choice of treatment depends on –
- The type of cancer you have
- The size and number of secondaries and where they are in the body
- The treatment you had already had
Surgery can be used in some situations to treat advanced bowel cancer -
- To slow the cancer
- When the bowel is blocked
- To remove secondary cancer
Surgery to control the cancer
Sometimes when there is a recurrence of bowel cancer in the bowel, it is possible to remove it. This is unlikely to cure the cancer because there are usually cancer cells elsewhere in the body. Removal of the bowel tumour may however relieve any symptoms you may have. It may also be some time before the cancer starts to grow anywhere else.
Surgery for blocked bowel cancer
Sometimes bowel cancer can grow so that it completely blocks the bowel. This is called a bowel obstruction. The waste from the food you have digested cannot get past the blockage. This can cause a number of symptoms such as feeling bloated and full, pain, feeling sick, vomiting, or constipation. To relieve symptoms, it is sometimes possible to unblock the bowel by putting in a stent.
Another way to remove an obstruction is to operate and remove the affected part of the bowel, provided you are fit enough. It may be possible to close up the bowel again during the operation or you may need to have a colostomy.
Surgery to remove small secondary cancers
If bowel cancer spreads, it often goes to the liver or lungs. Sometimes when the cancer secondaries in the liver or lungs are small and there are only one or two, you can have surgery to remove them. This is not suitable treatment in every situation and is done more often for liver secondaries than for lung secondaries. If you have this type of surgery, you may also have chemotherapy before and after the operation.
To decide if this treatment is suitable for you, your doctor will look at -
- Your general health
- How advanced your cancer was when you were diagnosed
- How quickly your cancer came back
- How many secondaries you have and their size
- Where they are in the liver or lungs
- How close they are to major blood vessels
Chemotherapy to shrink a cancer and control symptoms is called palliative chemotherapy. Treatment with chemotherapy at this stage is unlikely to cure your cancer, but it can help you live longer and may shrink the cancer.
For advanced bowel cancer, the aim of chemotherapy is to help you feel better. If however, you are unhappy about the side effects, you do not have to continue with the treatment.
How do you know if chemotherapy is working?
Your oncologist will arrange a scan before you start treatment and again three months later. Your oncologist can measure the tumour on the scan and so will be able to see how well the treatment is working. The tumour may have become smaller or larger or remained the same size.
If it has remained the same size, your oncologist will want to talk to you about whether or not it is worth continuing with your treatment.
If the tumour has become bigger, despite your treatment, your oncologist will stop the chemotherapy and may suggest trying a different treatment.
If it has become smaller, you may have a break and then have more treatment.
In Australia there are a number of government bodies responsible for the regulation and availability of bowel cancer treatments.
The Therapeutic Goods Act 1989, Regulations and Orders provide a national framework for the regulation of therapeutic goods in Australia to ensure quality, safety and effectiveness of medicines. They also set out the requirements for inclusion of therapeutic goods in the Australian Register of Therapeutic Goods (ARTG), including advertising, labelling and product appearance, for example.
The Therapeutic Goods Administration (TGA) is a unit of the Australia Government Department of Health and Ageing. It carries out a range of assessment and monitoring activities to ensure therapeutic goods available in Australia are of an acceptable standard. At the same time the TGA aims to ensure that the Australian community has access, within a reasonable time, to therapeutic advances.
All treatments used to prevent, cure or alleviate bowel cancer must be entered on the Australian ARTG before they can be supplied in Australia. Once approved and entered on the ARTG, they are available for human use and can be accessed privately.
Some treatments can then be recommended by the Pharmaceutical Benefits Advisory Committee (PBAC) to be listed on the Pharmaceutical Benefits Scheme (PBS) as a subsidised treatment. The Scheme is available to all Australian residents who hold a current Medicare card.
The PBAC is an independent statutory body established to make recommendations and give advice to the Minister for Health & Ageing about which treatments should be made available as pharmaceutical benefits.
No new treatment may be made available as a pharmaceutical benefit unless the Committee has so recommended.
The Committee is required by the National Health Act 1953 to consider the effectiveness and cost of a proposed benefit compared to alternative therapies. In making its recommendations the Committee, on the basis of community usage, recommends maximum quantities and repeats and may also recommend restrictions as to the indications where PBS subsidy is available.
When recommending listings, the Committee provides advice to the Pharmaceutical Benefits Pricing Authority (PBPA) regarding comparison with alternatives or their cost effectiveness.
Some treatments may not be recommended by the PBAC if they are deemed not cost-effective, even if they are clinically proven.
The issue of drug availability has received a lot of media attention and can be confusing and complicated. You should discuss all the options with your oncologist, and if a drug would be of benefit but it is not available via the PBS, you may consider accessing this privately or applying to a manufacturer to see if you are eligible to enter an access program or the drug made available on compassionate grounds.
Also, ask about clinical trials.
A list of the applications for consideration at each PBAC meeting is published six(6) weeks prior to each meeting. The sponsor of the submission will have already provided the PBAC with detailed clinical and economic data in support of the submission. However, you are welcome to provide comments from a personal (i.e. patient, carer, member of the public, health professional) or group perspective for consideration by the PBAC when the submission is considered.
Further details, including closing dates for input, can be found at www.health.gov.au.
In 25 May 2011 the Minister for Health and Ageing confirmed on Hansard that the Government is "concentrating on listing medicines on the PBS that treat serious and life threatening conditions where there are no alternative treatments on the PBS."
In doing so, the Government will rely "upon information provided by the PBAC in relation to clinical need for each medicine or vaccine, including whether alternative treatment options exist, and whether there were comparable listings in the past three years. Additional information taken into account is whether the listing provides expenditure savings and other technical information that the PBAC considered. The Government also relies on the expert advice from the Department of Health and Ageing and the Chief Medical Officer."
Any PBS listings with a financial impact will now have to be considered by Cabinet.
Scientists now understand that bowel cancer starts when the building "blue print" (the genes) for individual cells in the bowel are damaged and changed in some way.
Understanding how these abnormal cells behave means that doctors now also increasingly understand how the new cancer medicines available will work when bowel cancer spreads to other parts of the body.
They may be able to select an individual treatment plan for you that will have a better chance of success. Importantly, they may also be able to avoid giving you medicines if they know they won't work.
When would I have a KRAS test done?
Changes to the genes, identified as KRAS, usually happen slowly, in stages, to the same gene in the affected cells. The KRAS change occurs first, and is a useful marker when deciding which patients will respond to certain treatments for bowel cancer that has spread to other parts of the body.
If your bowel cancer has spread only to your liver and your liver surgeon believes that these tumours could be removed by surgery, then you should have this test done automatically.
You may also be able to ask to have the test done, if you have both liver metastases that can be removed and another limited area of potentially treatable, secondary disease.
Secondary bowel cancer can be treated with a range of medicines called monoclonal antibodies.
KRAS testing does not affect the way your chemotherapy is prescribed. Instead, it gives your oncologist the information they need to work out which other medicine from the monoclonal antibodies group may work for you.
Some monoclonal antibodies are given at the same time as your chemotherapy, whilst others are given on their own.
How are the tests done?
These tests are usually done on the cancer cells from the tumour or biopsy that was removed during your operation or endoscopy. Samples of the cancer will have been preserved and stored in the hospital laboratory. Your medical team will arrange for this tissue sample to be tested, which will confirm whether your tumour is -
- Wild-type KRAS (also called 'normal')
- Mutated KRAS
How long do the test results take to come back?
What are the treatment options once the KRAS status is known?
Around 40% of bowel cancer tumours that carry the KRAS gene mutation are referred to as KRAS positive tumours. Clinical studies have shown that patients with KRAS positive tumours may be successfully treated with the anti-VEGF therapy bevacizumab (Avastin), but do not respond to anti-EGFR therapy.
Some people with bowel cancer that has spread receive a monoclonal antibody, a type of biological therapy and are a different type of treatment to chemotherapy.
- ‘Monoclonal’ means all one type.
- ‘Antibody’ is a protein in your immune system that recognises and attacks foreign substances.
So a ‘monoclonal antibody’ is a treatment designed to recognise and target only one type of foreign substance (e.g. cancer cells).
The development of monoclonal antibody treatments is an exciting development in the treatment of cancer as it may be possible to kill cancer cells without damaging other healthy cells.
The monoclonal antibodies bind to bowel cancer cells. They interfere with cancer cell growth and the spread of cancer. People receive monoclonal antibodies through a vein at the doctor's office, hospital, or clinic. Some people receive chemotherapy at the same time.
During treatment, your health care team will watch for signs of problems. Some people get medicine to prevent a possible allergic reaction. The side effects depend mainly on the monoclonal antibody used. Side effects may include rash, fever, abdominal pain, vomiting, diarrhoea, blood pressure changes, bleeding, or breathing problems. Side effects usually become milder after the first treatment.
There are three Monoclonal Antibody (MAB) treatments for bowel cancer -
- Bevacizumab (Avastin)
- Cetuximab (Erbitux)
- Panitumumab (Vectibix)
These treatments seek out cancer cells that produce too much of a particular growth factor (a substance which stimulates a cell to grow and divide) and block the cell's receptors so the cell can't receive the signal to grow.
You might want to ask your oncologist these questions before having biological therapy –
- What drugs will I have?
- What will they do?
- When will treatment start?
- When will it end?
- How often will I have treatments?
- Where will I go for treatment?
- Will I be able to drive home afterward?
- What can I do to take care of myself during treatment?
- How will I know the treatment is working?
- Which side effects should I tell you about?
- Will there be long-term side effects?
Improving the lives of patients with bowel cancer through recognition of the value of prolonged, quality of life is one of the aims of the Bowel Cancer 2012 Challenge, presented to Government on 7 May 2009.
Some patients may be given radiotherapy as palliative treatment. In other words, it will be used to relieve the symptoms of the cancer or to reduce pain. Radiotherapy is not used much for colon cancers but may be used for rectal cancers. Internal radiotherapy may be used for secondaries in the liver.