Chemotherapy is not usually a single treatment. You have a course of treatment which includes a number of chemotherapy cycles. Your doctor may also refer to your treatment plan as your chemotherapy regimen.
Courses of treatment
A course of chemotherapy usually takes between 3 to 6 months, although it can be more or less than that.
The treatment will include one or more chemotherapy drugs. You may have the chemotherapy into a vein (intravenous drugs), or as tablets or capsules.
Cycles of treatment
During a course of treatment, you usually have around 4 to 8 cycles of treatment. A cycle is the time between one round of treatment until the start of the next.
After each round of treatment you have a break, to allow your body to recover. So if your cycle lasts 4 weeks, you may have treatment on the 1st, 2nd and 3rd days and then nothing from the 4th to the 28th day. Then the cycle starts again.
Or, as another example, you may have a 3 week cycle where you have treatment on the 1st and 8th days, but nothing on days 2 to 7 and days 9 to 21.
Why you have chemotherapy in cycles
Treatment plans are based on years of research. Your doctor will suggest the best combination of drugs based on the results of these trials. The drugs aim to kill the cancer cells while causing as little harm as possible to normal, healthy cells.
You have chemotherapy as a course of treatments over a few months because:
- it allows the chemotherapy to kill more cancer cells
- the rest between treatments allows your body to recover from any side effects
At any one time, some of the cancer cells will be resting. Chemotherapy only attacks cells that are in the process of splitting into two (dividing). So resting cells will not be killed.
Some of the cancer cells that were resting during your first treatment will be dividing by the time your second treatment comes around. So they should be killed off.
Normal cells usually repair the damage from chemotherapy more effectively than cancer cells. So damage to cancer cells should progressively build up without causing permanent damage to normal cells.
How often you have treatment
Depending on the drug or combination of drugs, each treatment can last a few hours or a few days. You may have treatments every week or every 2, 3 or 4 weeks.
How often you have treatment also depends on which drugs you are having, as well as your treatment plan.
When you have chemotherapy through an infusion pump, you may have the drugs:
- all the time for a few months (continuous administration)
- for a few days each month
- for a few weeks
Checks during your treatment
Before you have each cycle of treatment your doctor and nurse will check how you are. This includes finding out how you're coping with any side effects.
After a few cycles they'll also check how the treatment is working. Some people might need a change in their treatment plan. This change may be a delay before your next treatment or a reduction in the dose of chemotherapy.
Sometimes it can be difficult to assess whether chemotherapy is working. For example, if you’re having chemotherapy after surgery to remove cancer. This treatment aims to kill off any cancer cells that may have broken away before your operation. These cells are too small to see on scans.
How doctors choose your treatment
The exact treatment plan (regimen) that your doctor chooses depends on a number of things including:
- the type of cancer you have
- where it is in your body
- if it has spread and where to
Your doctor will also take your general health and fitness into account. Some drugs have more of an effect on your body than others. Your doctor has to judge that you're well enough to be able to cope with any side effects of the treatment before you start.
How often you have each cycle, and how long your treatment course lasts, also depends on many factors. These include:
- the type of cancer you have
- the drugs used
- how the cancer cells respond to the drugs
- any side effects from the drugs