Chemotherapy is the name given to treatments that use drugs to either kill cancer cells or control their rate of growth.
Chemotherapy drugs work by stopping cancer cells reproducing.
The drugs are carried in the blood so they can reach cancer cells anywhere in the body. Different drugs damage cancer cells in different ways. When a combination of drugs is used each drug is chosen for its different effects.
Chemotherapy drugs are also taken up by some healthy cells. These healthy cells can usually repair damage caused by chemotherapy but cancer cells can’t and eventually die.
The effect that chemotherapy drugs have on some of the healthy cells in your body can cause side effects. Most side effects will go away when treatment is over.
Healthy cells in certain parts of the body, such as the bone marrow (which makes blood cells) and the digestive system, are especially sensitive to chemotherapy drugs. This is why certain side effects, such as risk of infection or feeling sick, are more common.
Chemotherapy drugs are normally administered through a cannula inserted in your arm but there are also tablet forms. You can normally receive your treatment as an outpatient, although if it is your first time, you may be asked to stay in overnight just to check that you tolerate the treatment.
The drugs used, and any possible side effects, will be discussed in-depth prior to commencing any treatments and written information will also be given. You will be given many opportunities to ask questions.
Chemotherapy for NETs
There are many different types of NET and when considering chemotherapy treatments the following factors regarding the tumour must be taken into account:
- The organ the tumour started in. Tumours from the pancreas are more responsive to chemotherapy
- The type of tumour e.g. gastrinoma / carcinoid / insulinoma
- The growth rate or proliferation index (also called ki-67 index) of the tumour. Tumours with a ki-67 <4% are much less responsive to chemo.
- The pattern of spread of the tumour
These factors predict the biological behaviour of the disease and help to determine the likelihood of responding to chemotherapy.
Patient factors: Equally important with this decision making process is the assessment of the patient and the other potential options.
- If the patient has a lot of symptoms from their tumour this usually makes us more willing to offer chemotherapy.
- In order to cope with most types of chemo you need to be in reasonably good health, able to look after your self, with normally functioning heart, lungs, liver and kidneys and a reasonable exercise tolerance.
- Psychological well being. Long treatments like chemo can be quite stressful for some people, also some patients have a fear of chemo and be unwilling to try it.
Doctors and nurses always have to weigh up the pros and cons of the different treatment options available for any condition, but especially so for NETs where the different treatment pathways and options are so complex.
In essence we have to try and find the right treatment package for each patient and decide which is the right option at the the right time. If there is another treatment which is more effective or safer then we may try this first e.g. octreotide / surgery / embolisation / ablation. These treatment decisions always involve discussion with the patient. Before any final decision is made you have the opportunity to discuss this with the oncologist and your specialist nurse.
Types of chemotherapy:
1) Biological agents
These act to change the biological behaviour of the tumour cells, they are usually given in tablet form and they work by changing the internal processes in the tumour cells that control growth of the cells. Effectively they act to switch the cell off and make it dormant or inactive. This results in the tumour growing more slowly, stopping growing or shrinking. Sunitinib and Everolimus both act via different cellular pathways to produce this same effect.
2) Cyto-toxic agents
These act as toxins or poisons directly damaging and killing the tumour cells. They are most effective in fast growing NETs (ki-67>15%) as tumour cells are most vulnerable to chemo whilst they are growing. Streptozocin is an example of this kind of drug that is often recommended for fast growing NETs, often in combination with other cyto-toxic chemo drugs to try and magnify the effect.