Radiotherapy is the use of ionising radiation, otherwise known as X rays for treatment of cancer. The most common way to deliver radiation treatment is by external beam radiotherapy. High energy X rays are produced by a linear accelerator and are directed accurately through the body to the target area. For treating more superficial areas, lower energy X rays using a superficial or orthovoltage machine are used to spare deeper organs.
The first visit to the radiotherapy department is usually for treatment planning on a simulator. This is done by the radiographers (radiotherapy technicians), physicists and the cancer specialist (clinical oncologist). The treatment position and volume is determined and either an X ray or CT scan is taken. The radiographers may take some measurements and mark the skin with pen marks and several permanent tattoos. If the head and neck area is to be treated, a customised perspex shell may need to be made to immobilise the patient so that the treatment delivered is consistent from day to day.
External beam radiotherapy treatment is often given over a period of time depending on the total dose that is prescribed. Higher doses have to be divided into a greater number of treatments or ‘fractions’ to maintain an acceptable risk of long term side-effects and therefore take longer to complete. A typical course of treatment takes 4 to 6 weeks. Lower doses can be given in fewer fractions and over a shorter period of time.
Side-effects of radiotherapy can be divided into acute and late. Acute side-effects are defined as those experienced during or immediately after completion of treatment. Although acute side-effects can make getting through treatment difficult, they are usually completely reversible. The actual side-effects of radiotherapy depend on the site of treatment, the volume of normal tissue included and the radiotherapy dose given. During treatment, there is nothing to feel. Nausea and vomiting can occur within hours of radiotherapy if the stomach, bowel or brain is treated. Diarrhoea can occur within 1 to 2 weeks, sore skin and hair loss within 2 to 3 weeks. If large areas are treated, the blood count can be affected. During radiotherapy many patients feel tired and lethargic.
Late side-effects are usually not apparent for at least 6 months after completion of radiotherapy. However they tend to be permanent and are often progressive. For this reason, the clinical oncologist will take great care in the planning the treatment of radiotherapy in order to minimise the risk of late toxicity. In most cancers, there is a relationship between the higher the dose of radiotherapy given and the higher the expected tumour control rate (dose response curve). Therefore a careful balance between giving an adequate radiation dose to achieve maximal tumour control and not causing significant late toxicity is required. Despite the best techniques available, there are still risks of permanent side-effects and these will be discussed with the patient in order to gain informed written consent for the recommended treatment.
There is emerging evidence that when chemotherapy is given at the same time as radiotherapy (synchronous chemoradiotherapy), there is a radiosensitisation effect on both normal cells and cancer cells. This means that for a given radiotherapy dose, there is a greater proportion of cancer cell kill if the patient had been exposed to chemotherapy during this time than if radiotherapy was given alone. However the acute side-effects of chemoradiotherapy are often more severe. Chemoradiotherapy is used in routine clinical practice for cancers of the anus, oesophagus, cervix, rectum, pancreas, brain and head and neck.
Chemotherapy is the use of cytotoxic drugs to treat cancer. Chemotherapy can be delivered in several ways including:
Chemotherapy is usually given in cycles at 2 to 4 week intervals. The break in between cycles is to allow the body to recover from some of the toxic side-effects of treatment, in order to tolerate the next cycle. Depending on the type of cancer, a combination of 2-3 drugs is often given as higher response rates may be achieved.
Side-effects of chemotherapy are related to the type of drug given, dose and frequency of administration. The commonest side-effects encountered by patients having chemotherapy are nausea and vomiting, hair loss and a low blood count. The blood count can be affected by one or a combination of 3 ways; (i) low red blood cells or haemoglobin (anaemia) causing tiredness, pale complexion and breathlessness, (ii) low white blood cells will make the body more prone to developing infections, (iii) low platelet count increases the risk of bruising and bleeding.
Low white blood cells (neutropenia) do not cause any symptoms until an infection develops. The symptoms of infection (neutropenic sepsis) include fever and rigors (shivers). In addition there may be more specific symptoms related to the source of infection such as diarrhoea, cough or cystitis. It is vital for any patient who is having chemotherapy to seek immediate medical attention if they develop any of these symptoms. They will need to be thoroughly assessed and have an urgent blood count. All patients with neutropenia and fever will be admitted for intravenous antibiotics with few exceptions. If treatment for this is delayed, there is a serious risk of rapid deterioration into shock and even death. For this reason patients are generally advised to contact the Cancer Centre under which they are receiving treatment rather than to see their general practitioners.