Radiotherapy is the use of high energy rays, usually X-rays, to kill cancer cells. It is used to either get rid of the cancer (curative) or to reduce pain and other symptoms (called ‘palliative radiotherapy’).
External Beam Radiotherapy (EBRT) as a curative treatment for cancer has been used for many years with good success. Cancer cells differ from normal body cells in that they reproduce faster and are thereby more susceptible to high energy rays. In consequence repeated exposure to high energy rays will kill off cancer cells but allow normal cells to recover. Not all cancer cells act in the same way, however, so it is necessary to adjust the exposure and duration to achieve optimum effect. The treatment itself is painless. It normally involves daily attendance, 5 days a week, at a radiotherapy centre for short sessions for up to 7 weeks.
External Beam Radiotherapy is also used as an additional treatment, either in cases where post-surgery pathology has identified a positive surgical margin (see p. 17) or where other treatments have not been totally successful, and the cancer has recurred. This has been shown to improve overall survival.
For prostate radiotherapy, short-term side effects such as bladder or rectal irritation, tiredness and nausea, are common. Long-term side effects can include alteration of bowel habit and impotence problems. As with other treatments, ejaculatory function is either lost or degraded. Because of damage to adjacent tissues, there is now some evidence of a small risk of developing bladder or rectal cancer 10 or more years after treatment.
These side effects should be discussed in detail with your consultant oncologist prior to your agreement that the treatment should proceed.
Over the past few years there have been substantial advances in the methods which have been used to apply radiotherapy.
Conformal radiotherapy, (see drawing on left) has been in common use for some time. The radiation beam is shaped to reduce the radiation to the surrounding areas, but it is unable to provide the detailed targeted 22 coverage that newer technologies can offer.
Intensity Modulated Radiation Therapy (IMRT) and Image Guided Radiation Therapy (IGRT) equipment (see picture below) takes conformal radiotherapy a step further in the precision in which the beam is shaped and directed at the body, typically from five different angles. A high degree of planning and computer control is involved in these processes, requiring more time in the treatment sessions. These methods help to reduce some of the side-effects listed above. Although not yet widely available in the UK, this new equipment is impressive, with good short-term results. The National Radiotherapy Advisory Group has stated that by 2012 IMRT should be available in at least one centre in each Cancer Network. Currently only a limited number of NHS prostate cancer patients have been able to access this new equipment.
'Cyberknife' (see picture below) is the very latest device to deliver radiotherapy to patients. The device differs from its gantry cousin IMRT and conventional Conformal radiotherapy, in that the radioactive substance is contained in a robotic arm, thus giving the advantage of being able to direct the radioactive beam to any part of the patient with greater accuracy, higher intensity and avoiding, to a large part, even greater collateral damage to nearby healthy tissue.
'Cyberknife' can treat complex tumours wrapped around sensitive structures such as nerves or blood vessels, where surgeons cannot operate. A small linear accelerator is mounted on a robotic arm which manoeuvres with exceptional agility around the patient, and a scanner tracks the tumour when the patient moves.
There are a few centres in the UK that have a 'Cyberknife' capability. The Royal Marsden Hospital is one that is available to NHS patients, though funding may not always be possible. There are others at private centres.
This is measured in Grays (Gy). Depending on clinical indications, for Conformal radiotherapy 74 Gy in daily 2 Gy doses or ‘fractions’ is used to the prostate. After prostatectomy, 66 Gy is used. There is evidence that increased dosage over a shorter period has some benefits. This is called hypo-fractionation, and is still the subject of some controversy. Increased dosage can also be given with latest IMRT machines, where damage to surrounding tissues (e.g. bladder and rectum) is considerably reduced.
Curative radiotherapy can normally only be applied once so, if there is a re-occurrence of the cancer at the same site, which is unusual, an alternative treatment method (such as hormone therapy or possibly cryotherapy or HIFU has to be applied. Subsequent surgery at the radiated site is rarely possible. Hormone treatment is also often used to shrink the cancer before radiotherapy starts. This also helps reduce the risk of recurrence.
Radiotherapy is sometimes used for the treatment of bone pain associated with secondary tumours (called palliative treatment). Treatment at a different dosage is given to the affected bone or area. Many men notice some pain relief within a few days whilst for others the relief may take several weeks to become effective. The radiotherapy may be given as a single treatment (usually of 8 Gy) or as several smaller treatments. If the cancer has spread to several areas, a treatment known as ‘hemibody irradiation’ is applied over a larger area. Although this is now very seldom used, it normally gives good pain relief. The side effects, however, can be somewhat severe.
Note: When receiving radiotherapy, it is important to follow the dietary advice given by your radiologist.