Introduction

Radiotherapy has been a key treatment for cancer for over a century and although the fundamental principles of treatment have not changed, the method of delivery and the treatment techniques have changed considerably. Most patients diagnosed with cancer undergoing radiotherapy will receive their treatment as an outpatient, so you may meet them in the community setting or in an outpatient unit, or on a ward if they are admitted for a treatment-related problem or other medical condition. Radiotherapy remains misunderstood by patients and it is often feared due to association with radiation disasters and misuse. It is important while on a cancer/palliative placement that you make the most of the opportunity to understand this treatment; arrange an insight visit to the radiotherapy department to observe the equipment and to understand the complexity of planning radiotherapy and to appreciate the experience of patients.

After surgery, radiotherapy is the most effective curative treatment for cancer (Burnet et al 2000). Approximately 50% of patients in the UK will receive radiotherapy. Unlike the treatments discussed in previous chapters that are given systemically, the value of radiotherapy is in the local management of cancer. The success of radiotherapy is dependent on how bulky the tumour is, how sensitive the tissues are to radiation and the location of the tumour.

Radiation is a natural part of the electromagnetic spectrum. At one end of the electromagnetic spectrum are radio waves which have low energy and bounce around us; at the other end of the spectrum, X-rays, beta and gamma rays are highly energised and can penetrate into the body, causing ionisation. Ionisation is where the atoms within the cell are altered by the radiation. Atoms are electrical in nature. When they come into contact with radiation, the highly energised waves from the radiation cause an orbiting electron to be dislodged and join an adjacent atom which is said to be ionised (Fig. 13.1).

Fig 13.1 Ionisation of atoms

Whether an atom has lost or gained an electron, the atom becomes unstable and the cell DNA becomes damanged (especially when the cell is dividing), causing the cell to die. Similar to cytotoxic drugs, radiotherapy will damage and kill healthy cells as well as cancer cells. Normal cells have the ability to repair and replace themselves when they are damaged though.

X-rays, beta and gamma rays have the right amount of energy to produce ionisation in atoms, which takes place as radiation passes through tissue. Different tissues have different levels of sensitivity to radiation. This will affect the success of the treatment but also restricts the dose that can be given.

Radiotherapy is measured in Grays (Gy), the amount of radiation absorbed by tissues (1 Gy = 1 joule of energy absorbed per Kg of tissue). Cancers that are radio-sensitive (lymphomas, germ cell cancers) are given lower doses (20–45 Gy), while those that are radio-resistant (gliomas, prostate, adenocarcinomas) are given higher doses (60–70 Gy).

External beam radiation is the commonest type of radiation treatment. It is given in the outpatient setting using beams of radiation that are artificially made by accelerating X-rays using a machine called a linear accelerator (Linac).

There are four principles (‘four Rs’) that support our understanding of how radiotherapy works:

• Repair: radiotherapy damages cells both directly and indirectly. Directly, if the damage to DNA is great, the repair genes will not be able to fix the problem and the cell will commit suicide or undergo apoptosis. Indirectly, the radiotherapy interacts with oxygen and water molecules in the cell to damage DNA as it is synthesised. Very few cells are killed straight away – it takes several cell divisions before the cell dies. Cells that die immediately are very radiosensitive, such as lymphocytes and germ cells. These are very vulnerable and responsive to radiotherapy.

• Reoxygenation: the success of radiotherapy depends on the presence of oxygen. Many cancers have a poor blood supply and are often hypoxic. This reduces the indirect action of radiotherapy which requires oxygen to damage the synthesis of DNA. To maximise the amount of oxygen, external radiotherapy is generally given in fractions. These are individual doses of radiotherapy which allow well-oxygenated cells to be killed, making way for hypoxic cells to have access to more oxygen, making them more sensitive to the next fraction of radiotherapy. Fractionisation also allows normal cells to repair and repopulate which minimises side effects.

• Redistribution: those cells in G0 will not be killed initially as they are not actively in the cell cycle, but as cells that are actively cycling die, cells in G0 are recruited into the cell cycle to replace damaged cells. Giving fractions over a period of days/weeks means that cells are more likely to be in the cell cycle and be killed. Cells are most sensitive in the M and G2 phase.

• Repopulation: cancer cells that are not actively dividing when the radiotherapy is given will start to divide after the dose, in order to replace those cells destroyed. If another dose of radiation is given, these cells will also be damaged. If the cancer repopulation happens more quickly than the radiotherapy is given, the success of the treatment will be reduced. For example, when radiotherapy is given, a number of cancer cells are killed off and other cancer cells repopulate to replace those lost. If there is a delay in the treatment schedule, these cancer cells will continue replicating, reducing the chance of success. Some radiotherapy schedules, such as accelerated hyperfractionated (CHART) radiotherapy, are give twice a day to try to deal with the problem of cancer cells repopulating more quickly than normal cells.

Careful planning of radiotherapy is essential to maximise the effects and minimise the damage to sensitive surrounding tissues and this may take time and delay treatment. X-rays and magnetic resonance imaging (MRI) scans are used to identify the location of the cancer. These scans are loaded into a planning computer to ascertain the shape and size of the treatment field. To minimise the damage to sensitive structures and tissues, the smallest area possible is treated. Shields and moulds are used to shape the beams and control the depth of penetration. A mask may be made if an area of the body needs to be immobilised to ensure precision, such as the head and neck. The dose and number of fractions are calculated and a machine called a simulator (a diagnostic X-ray machine) is used to give a dry run to check the accuracy and to make any adjustments. The information from the simulator is then used by the radiographer to deliver the radiotherapy exactly as planned.

Activity

Visit the radiotherapy department and watch how a mask for head and neck radiotherapy is made. Find out how a patient’s radiotherapy is planned using the simulator. Escort a patient to radiotherapy. Find out about how the patient is positioned and how the machine is set up. If you are in a clinical area where this does not happen, discuss with your mentor about arranging a spoke placement or an insight visit to observe radiotherapy being planned and given.

NMC Domain 3: 3.1; 3.2; 3.4; 3.6

Seeing this for yourself will help you to reassure patients who are undergoing radiotherapy that you might meet while on another placement.

External beam radiotherapy is particularly good in the management of symptoms. Because of the way radiation works, the cells do not immediately die and the treatment may initially cause exacerbation of symptoms, which may increase distress and anxiety. Many patients experience bone pain (often caused by bone metastases). Bone pain is often unresponsive to pharmaceutical drugs but generally is responsive to radiotherapy. Radiotherapy to the site(s) of the cancer in the bone will kill the cancer cells and stimulate new bone growth. It takes several days, and up to 2 weeks before the full benefit is achieved and pain is reduced. During this time, the level of analgesia should be maintained and the patient should be informed that there will be a delayed response.

Activity

Read Rosenfield and Stahl (2006) (see References). Discuss the role of radiotherapy and the use of other strategies used to manage bone pain, and the nursing implications for each, with your mentor