External Beam Radiotherapy
Radiotherapy is the use of high energy rays, usually X-rays, to kill cancer cells. It is used:
(1) with the aim of getting rid of the cancer (curative radiotherapy)
(2) after or in conjunction with another treatment if there is a doubt whether the treatment has been successful, or
(3) to reduce pain and other symptoms in advanced cancers (called ‘palliative radiotherapy’).
Cancer cells differ from normal body cells in that they reproduce faster and are thereby more susceptible to high energy rays. So 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, 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.
Radiotherapy has been proven to improve overall survival in treating locally advanced disease, and is an alternative to surgery for those men with localised prostate cancer. It may be recommended to men with adverse results after surgery as an additional treatment. Compared with hormone treatment alone, radiotherapy halves the risk of dying from prostate cancer.
Side effects of radiotherapy (see also Side Effects)
For prostate radiotherapy, the short-term side effects can be bladder and/or rectal irritation, including blood in the urine or rectum. 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.
This has been in common use for many years and, until recently, has been the standard method of delivery for prostate cancer patients. The radiation beam is shaped to reduce the radiation to the surrounding areas, but it is unable to provide the detailed targeted coverage that newer technologies can offer.
Intensity Modulated Radiation Therapy (IMRT) and
IMRT and IGRT take 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 equipment is impressive, with good short-term results. The National Radiotherapy Advisory Group has stated that IMRT should be available in at least one centre in each area. NHS prostate cancer patients are nowbecoming more able to access this new equipment.
Stereotactic Radiotherapy (Cyberknife)
‘Cyberknife’® is one of several types of radiotherapy machine that delivers stereotactic radiotherapy. This form of radiotherapy uses pencil-like beams of radiation that are directed from different angles precisely on to the tumour. The X-rays are contained in a robotic arm, thus giving the advantage of being able to direct the beams 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. The scanner moves with exceptional agility and is able to track any slight movement of the patient or his prostate.
|Sterotactic treatment is able to treat complex tumours wrapped around sensitive structures. It is used for a number of cancers where precise targeting is essential, and it is undergoing a trial for special prostate cancers that would benefit from this treatment. Fewer treatment sessions than for conventional radiotherapy are generally needed. However, it has not yet been proven whether this method is any safer or better than IMRT.|
There are currently only a few NHS hospitals and private clinics in the UK that have CyberKnife®. These include the Royal Marsden Hospital and London clinics.
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. Increased dosage over a shorter period in conformal radiotherapy has been shown to have detrimental results. However, increased dosage can be given with the latest IMRT machines, where damage to surrounding tissues (e.g. bladder and rectum) is considerably reduced.
What happens should radiotherapy fail?
Curative radiotherapy can only be applied once so, if there is a re-occurrence of the cancer at the same site, an alternative treatment method (such as hormone therapy or possibly cryotherapy or HIFU) has to be applied. Subsequent surgery at the radiated site is difficult and is only undetaken by specialised surgeons. Hormone treatment (see Hormone Therapies) can be, and is often used to shrink the cancer before radiotherapy starts. This also helps reduce the risk of recurrence.
Palliative radiotherapy and bone pain
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 bone or area affected. 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 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.
Advantages and disadvantages