External beam radiotherapy for prostate cancer involves sophisticated machinery (linear accelerators) and highly trained medical staff (radiotherapists, radiation physisicists and radiographers).
Planning and scanning | Side effects of radiotherapy treatment |
Simulation | Results |
Treatment | |
Radiotherapy planning involves the determination of the area within the body that requires treatment and the calculation of radiotherapy dosage that is to be applied to the treatment area.
Computerised information concerning the prostate's position, size and shape are acquired from the CT scanner and used to develop a radiotherapy plan, involving multiple beams. These beams will be directed at the prostate from different directions and the planning information acquired at the planning CT scan allows this process to be optimised.
We refer to the 'bespoke' radiotherapy planning for each individual as 'conformal radiotherapy'; there are several types of conformal radiotherapy (of which one is intensity modulated radiation therapy). Computerised imaging allows the precise identification of other internal organs, such as the rectum. This precision in imaging, plus the advantages of modern conformal radiation therapy techniques, helps considerably in reducing the radiation dosages to normal tissues, such as the rectum, and allows the radiotherapy to be given more precisely to the prostate itself.
At this planning stage, it is customary to place 'dot' tattoos on the patient's skin surface as orientation marks from which the radigraphers 'set-up' each day's treatment
The next step in the radiotherapy treatment process is called ‘simulation’ and this is a dummy run for the real treatment. The patient is filmed through the radiation portals that have been planned to treat him; these films are then checked for precision - i.e. the patient does not start the radiotherapy until the planned fields (radiation portals) have been verified.
The linear accelerator used to treat patients with radiotherapy looks like a little like a diagnostic scanner (see fig). A radiographer positions the patient on the treatment couch. The radiographer then orientates the radiotherapy machine treatment head in the correct position, aligning the tattoo that has been applied with the head of the machine using laser beams.
The radiographer will then leave the treatment room, having asked you to keep as still as you possibly can. The staff will observe you from the machine control, using a video camera. After a few moments radiotherapy treatment is given. The radiation, which takes the form of energy waves, will leave no impression upon you. You will not notice that it has been given. After less than a minute you will be allowed to get up from the treatment couch and leave hospital.
The most common treatment plans involve daily treatment, apart from weekends, for a period of 7+ weeks. In some centres treatment is given to higher dosages and this may require either multiple daily attendances or a more protracted treatment course. The majority of people continue a normal life through treatment.
SELECTION OF PATIENTS FOR RADIOTHERAPY: Immediate radiotherapy is reserved for those patients without evidence of disease outside the prostate, as determined by a pelvic MRI scan - these are given stage of T1 or T2 disease.
Thus, patients with a biopsy proven prostate cancer and no disease through the capsule of the gland can move straight to curative radiotherqpy.
Where there is evidence of early spread throught the capsule of the gland (e.g. capsular breach on the MRI or disease into the seminal vesicles) then it is nowadays usual to start therapy with anti-hormonal therapy to shrink (down stage) the cancer - i.e. shrink it back down into the gland, thereby rendering it more radiocurable by radiotherapy.
In such patients, it is nowadays common to continue the anti-hormone therapy for up to 2 years after the radiotherapy, as several trials have shown this to be in the interests of patients who present with this so-called T3 disease, (T3 disease is the stage given to the cancer where it has breached the capsule of the gland). Such longer term endocrine therapy further improves the disease free figures in this slightly higher risk group of patients.
Cystitis and urethritis
The most common form of side-effect is due to the effects of radiotherapy on the bladder base, which lies just above the prostate and is manifest by a need to void urine more frequently than normal with sometimes a little discomfort. These symptoms are absent in the first several weeks of therapy and come on in the last two weeks of therapy, tending to recover 1 – 2 weeks after the completion of radiotherapy.
Cranberry juice (as a substitute for citric acid juices) is useful to ameliorate this symptom and effercitrate tablets (dissolved in water and drunk three times a day) are the best at reducing this symptom.
Proctitis
The other normal organ that is affected by radiotherapy is the rectum and the time course of these effects is very similar to the effects on the urethra. with increased call to stool in the last few weeks of therapy and, in patients with haemorrhoids, a tendency to blood streaking on the stools at defaecation.
Impotence
Two thirds of men retain sexual potency at the status quo ante level.
The effects of the radiotherapy on potency can be improved by a number of artificial means. Probably the easiest treatment for potency loss is Sidenafil, which is popularly known as Viagra.
When adjustments are made for patients who have been turned down for surgery or brachytherapy, because of transcapsular spread or other higher risk features, then the results of modern conformal external beam radiotherapy are comparable with the best results of radical surgery or brachytherapy.
For some patients with risk factors slightly too high for brachytherapy alone (i.e. as monotherapy), external beam conformal radiotherapy is used in conjunction with brachytherapy - the perceived advantage of this being that there is a slightly wider field of coverage from the external beam component but still the great big 'oooomph' of radiatio therapy to the central disease from the brachytherapy component .
