Information about surgery, personalised treatment options and side effects.
Identifying Risk Factors
Chemotherapy or “chemo” includes drugs that disrupt the life cycle of the cancer cells and their aim is to kill or at least harm the tumour cells.
The types of chemotherapy differ in the way they work. Some kill cancer cells by damaging their DNA whilst others interfere with cell parts that make new cells so that no new cells are made.
Chemotherapy drugs used to treat colorectal cancer may be administered differently. They can be administered orally, by mouth (oral chemotherapy) or injected into a vein (intravenous chemotherapy).
Chemotherapy will mostly be administered through a vein intravenously (IV) and therefore once in the bloodstream it can travel throughout your body to treat cancer. But it can also be given orally, in pill form.
Chemotherapy is given in cycles of treatment days followed by days of rest. Depending on which drugs are used the cycles may vary (common cycles are 14 to 21 days).
Safe intravenous access
To make these treatments easier you might have a medical device called a catheter or port attached to your hand.
Sometimes the team may suggest using a bigger catheter. This goes into a large vein.
Your doctor may put this type of catheter completely under the skin. If so, it is connected to a small plastic or metal disc called a port. The entire device is called an Implantable Venous Access System.
Ports can remain in place for weeks, months, or years. Your team can use a port to reduce the number of needle punctures, give treatments that last longer than 1 day (the needle can stay in the port for several days), give more than 1 treatment or medication at a time and do blood tests and chemotherapy the same day.
Oral chemotherapy is a drug taken in tablet, capsule or sometimes a liquid form. It has the same benefits and risks as chemotherapy given by infusion. As you can take oral chemo at home you don’t need to go to a hospital or clinic for every treatment. It is very important to take your pills just like your doctor or nurse tells you to.
Chemotherapy Treatment Lines
Neo-adjuvant and adjuvant chemotherapy
It is possible that you will receive chemotherapy prior (neo-adjuvant) and after surgery (adjuvant) depending on the stage of your tumour.
The aim of neo-adjuvant treatment is to shrink a tumour so it can be fully removed during surgery. The aim of treatment in an adjuvant setting is to prevent the cancer from recurring.
You can explain this type of treatment by comparing it with weeding.
Weeds grow in the garden. They must be removed. However, for various reasons, weeds often grow
back probably because they were not removed completely and part of their roots stayed in the soil.
The left-over roots allow them to grow again. That’s why we use weed killers.
Let us go back to the tumour full of cancer cells. You ‘remove’ the tumour during surgery (weeding) but to prevent that cancer cells growing again you need an extra treatment -chemo and/or radiotherapy (weed killers).
Next treatment lines
The initial treatment is referred to as first-line treatment or first-line therapy. It is usually what worked best in clinical trials for patients with the same type and stage of cancer.
How well your treatment works often varies. A first-line treatment may not work, may start but then stop working, or may cause serious side effects. Your physician may then suggest a second-line treatment also called second-line therapy. It is a different treatment but it is likely to be effective.
There are factors that affect whether second-line therapy may work such as the stage of your colon cancer, if you experienced side effects during the previous treatment and of course your overall health.
If you need a second-line treatment this does not mean that you did not get the right treatment the first time or that there are no more treatments to try.
Third-line therapy or additional rounds of treatment
As well as the first-line therapy, the second-line treatment may not work, may have had an effect but then stopped working or may cause serious side effects that need treatment discontinuation.
It is possible that your doctor will discuss with you the opportunity of a third-line therapy or additional rounds of treatment. Depending on the available drugs in your country you may be able to have another line of treatment.
Taking the time to review all possible options for care may help you feel more comfortable in making your decision about further treatment.
The mainstay of chemotherapy for colorectal cancer is treatment with cytotoxic drugs called fluoropyrimidines, given either as single therapy (called monotherapy) or in combination with other drugs (called combination therapy).
In combination chemotherapy fluoropyrimidines are combined with other chemotherapeutic drugs such as oxaliplatin or irinotecan.
Side Effects of Chemotherapy
Side effects of chemotherapy are frequent even if progress has been made in controlling them using adequate supportive measures. They will depend on the drug(s) administered, on the doses, length of treatment and on individual factors. If you suffered from other medical problems in the past some precautions should be taken and/or adaptation of the treatment should be made.
Listed below and in the table above are the side effects that are known to occur with one or several of the chemotherapy drugs currently used for colorectal cancer. The nature, frequency and severity of the side effects vary for every chemotherapy combination used. Some can be very serious while others can be unpleasant but not serious.
Most side effects appear shortly after treatment starts and will stop (several days) after treatment. Other side effects however are long-term or may stay permanently or appear years later.
The most frequent general side effects of chemotherapy are:
- Decreased blood cell counts
- Decrease in white blood cells (neutropenia) leading to higher risk of infection
- Decrease in platelets (thrombocytopenia) leading to easy bruising and bleeding
- Decrease in red blood cells (anemia) leading to fatigue
- Fatigue which may be prolonged
- Nausea or vomiting
- Sore mouth or mouth ulcers
- Hair loss
How Targeted Therapies Work
In contrast to cytotoxic chemotherapy, targeted therapy is cytostatic, it does not kill, but mainly blocks the rapid increase in the number of cancer cells by interfering with specific factors, for example growth factors and growth factor receptors.
Blocking growth factors and receptors
Growth factors are chemicals produced by the body that control cell growth. There are many different types of growth factors and they all work in different ways.
These growth factors are also present in normal tissues, but they are often changed (mutated) or over-expressed (too many) in tumours.
Growth factors work by binding to receptors on the cell surface. These receptors, like antenna, pick up growth signals and send a signal to the inside of the cell. This sets off a chain of complicated chemical reactions that prompt the cells to grow and divide.
Cancer cells often have with too many of these receptors, can pick up too many growth signals, then ‘transmit’ the signals to the inside of the cell and end up growing and multiplying uncontrollably.
Targeted therapy drugs block growth signals either on the outside of the cell by blocking the antenna or on the inside of the cell or by blocking the signal pathway. This is called inhibition – the act of stopping or slowing down a process.
Either way, by blocking the signals the growth will be interfered with.
You can compare this mechanism with the underground (metro)…
Imagine that you need to take the metro to go from one place to another. It might be possible that the entrance to the station (receptor) is blocked, you cannot enter and you need to wait until the door opens. It might be possible that you can enter the station but that the carriage (wagon) is out of order (your path is blocked) again you need to wait and you cannot get to your location.
Types of growth factor
There are a number of different growth factors and receptors.
- Epidermal growth factor (EGF) – Epidermal growth factor receptor (EGFR) – Some people with colon cancer have abnormal changes in their genes that control the epidermal growth factor receptor. These changes may cause the cancer cells to have too many receptors or they may be too active thus causing new cancer cells to develop quickly.
- Vascular endothelial growth factor (VEGF) – Vascular endothelial growth factor receptor (VEGFR) – controls blood vessel development. The growth of new blood vessels is called angiogenesis. New blood vessels are constantly forming in the body to heal wounds and repair damaged tissues. In females angiogenesis also occurs during the monthly reproductive cycle. The body controls angiogenesis by balancing stimulatory (activators) and inhibitory (inhibitors) factors. Cancer cells need food and oxygen in blood in order to grow that is why the tumour sends chemical signals (such as VEGF and its receptor) which in turn stimulates blood vessel growth and therefore allowing it to grow rapidly.
Types of targeted therapy
- Monoclonal antibodies are mostly are administered intravenously
- Small molecule inhibitors are usually taken orally, in a pill form
These are either given as single therapy (called monotherapy) or in combination with chemotherapy (called combination therapy).