BrachyTherapy Treatment Option
What is brachytherapy?
Brachy comes from the Greek root meaning short. Brachytherapy means that the radiation travels a short distance into the tissues, whereas with an external beam source the radiation must travel a long distance to reach its target tissue. In essence with brachytherapy the source of radiation is implanted directly into the tissue to be irradiated.
The oncologist can vary certain parameters:
The dose of the radiation by changing the number of seeds used or by charging the seeds to a particular level of radiation.
The energy delivered to the tissues by changing the radioactive material.
The period of radiation by altering the radioactive isotope.
The field of radiation by the particular placement of seeds.
Different cancers respond to different forms of radiation treatment. Oncologists have learnt through trial and error what type of radiation is best for each particular cancer.
What types of brachytherapy are available for prostate cancer?
There are basically two forms of brachytherapy.
a) Low dose brachytherapy (LDR)
Low dose brachytherapy is the conventional method whereby radioactive seeds are placed permanently into the prostate gland. In prostate cancers the commonest seeds used are radioactive iodine or palladium. These deliver a low dose of radiation over a period of several months. After a certain time, determined by the isotope, they become inactive. There has never been a report that these seeds can cause any harm over the long term. The method by which the seeds are placed is critical and will be discussed further on in the text.
b) High dose brachytherapy (HDR)
This treatment is not commonly used. It is available only in certain academic institutions. In this form of treatment high dose iridium rods are temporarily placed in the prostate gland for a few minutes. The dose is repeated every six hours until four doses have been given. This form of treatment is used in patients who for some technical reason cannot have LDR therapy. Safety protocols are much more stringent because the radiation is more dangerous. Also the treatment is far more involved technically, requires expensive auxiliary equipment and additional trained personnel. The treatment takes longer and additional external beam radiotherapy has to be given as well.
How are the seeds placed?
In the early nineties a technique to place seeds permanently in the prostate gland was developed. The patient would have the prostate gland imaged carefully prior to the seed placement procedure. The oncologist would then design a plan to place seeds in the prostate according to its dimensions. The seeds would be ordered and the patient would have his procedure about a week later. The patient went to theatre, was anaesthetised and the seeds then inserted through the perineal area into the prostate gland. However what was not well understood was the issue of prostate mobility. Needles were inserted into the prostate gland without direct visualisation of the gland. The needles were inserted according to the position of the gland on the pre-plan scan. Inserting needles into a prostate gland can change its shape and move it up to 20 mm in a headwise direction. The result was that needles were now not positioned correctly and the seeds were therefore placed in the wrong position. This led to damage to surrounding organs and cold zones within the prostate gland. Side-effects where thus common including serious side-effects. Cure rates were not excellent. Amazingly many centres continue to use this technology.
The next major advance came with combining the pre-planning stage with the actual seed implant. Again however the seed placement was based on indirect visualisation of the prostate gland. The position was inferred from x-ray imaging of the bladder base rather than direct visualisation. A system designed by Stock and Stone of the USA improved the method by introducing rectal imaging and visualising the needle insertion into the prostate gland. Their system was commercialised but it falls short when it comes to source insertion and again seeds are not placed accurately. Surgeons who do salvage prostatectomies on patients treated with this technique report that the seeds are very erratically placed. However hybrid techniques are widely used and the world literature reports good results.
This is now the gold standard that units offering brachytherapy should strive to master. Using this system, each seed is visualised as it is placed and the position exactly matches the plan that the surgeon set out to achieve. A system of checks and balances ensures that if a seed is inadvertently placed incorrectly then the plan will adapt to reposition other seeds so the radiation cover is uniform. The end result is a seed placement as close as possible to the ideal treatment plan.
Who can have brachytherapy?
Brachytherapy is an alternative to radical prostatectomy as the treatment of choice to cure patients with localised prostate cancer. The latest twelve year published data show that brachytherapy achieves excellent results comparable to surgery. Even radiation oncologists will agree that external beam radiotherapy does not provide equivalent results for long-term cure. Basically the same criteria as for radical prostatectomy apply to the use of brachytherapy. There are some technical differences which will be discussed. First and foremost the patient must have localised disease. There is no point in treating a patient locally when the horse has already bolted from the stable. The majority of patients will not have any local symptoms and so a systemic form of treatment with minimal or no side effects on urination should be rather given. Prostate glands larger than 40 gm should ideally be shrunk prior to brachytherapy using a short course of hormonal therapy over three months. With real time brachytherapy this is no longer an essential requirement because the technique solves several technical problems involving large glands. Patients with significant bladder obstructive symptoms, clinical evidence of bladder obstruction or with large prostate middle lobes should not have brachytherapy because of the high risk of urinary retention. A TURP procedure can be done prior to brachytherapy to relieve the obstruction if real time brachytherapy is going to be used.
There should be a period of eight weeks between treatments to allow the prostate gland to heal. Also the TURP procedure should be minimal in extent otherwise needle placement can become impossible. After a TURP a prostate must be carefully examined to assess if brachytherapy is still possible and safe to perform. Patients with disease more advanced than T2b have traditionally not been considered good candidates for radical prostatectomy by careful surgeons. However there is an evolving place for treating patients with t2c or even T3 disease with brachytherapy in combination with external beam therapy and hormonal therapy. Age is still considered by many people to be important in the type of treatment offered. Young people tend to have very aggressive disease and it is strongly felt their glands should be removed. However now that twelve year data reveal that radical prostatectomy and real time brachytherapy are equivalent in outcomes this argument is no longer valid. It is safe for young people with prostate cancer to have brachytherapy.
What are the Side-Effects?
Brachytherapy including real time brachytherapy is not without side-effects. The majority of patients receiving real time brachytherapy will experience minimal post treatment symptoms.
Side-effects that can be expected include:
Reduced urine flow due to swelling of the gland in the first few months. All patients are put onto a medication to counter this problem.
Increased urgency and frequency due to radiation irritating the sensory nerves in that region.
Pelvic pain especially when seeds are placed too laterally.
Urinary retention, fortunately not common, is a nuisance to manage and can have a profound effect on the patient. Many will improve once the prostate swelling resolves.
Loose frequent stools from rectal mucosal irritation.
Reduction in ejaculate volume with time as the prostate gland fibroses.
Orgasmalgia: this is a medical term denoting pain with orgasm; bloody semen (haematospermia); and reduced intensity of orgasm occur fairly frequently. Orgasmalgia tends to subside after the first year. Haematospermia resolves soon after the resumption of sexual intercourse following brachytherapy. It may occur again later with radiation changes occurring in prostatic blood vessels.
Accelerated loss of erectile function compared with other ageing males who have not received radiotherapy. Figures of between 52 to 76 % potency rates are reported at six years after treatment. It would seem that patients who are going to get erectile dysfunction will already be reporting this issue by twenty four months after the procedure. Older men receiving the radiation tend to have a greater fall-off in erectile function. The addition of hormonal therapy also increases the risk of erectile dysfunction. Regular sexual stimulation after brachytherapy helps to prevent erectile dysfunction.
Severe complications such as rectal fistulas, urethral stricture, incontinence and penile irradiation are associated with pre-planning techniques and over dose of radiation to the involved organs.
How is Brachytherapy performed in our institution?
The patient is anaesthetised and placed in the lithotomy position and the rectum washed out. A catheter is inserted into the bladder.
A sonar probe is placed inside the rectum and the prostate gland is visualised.
The images are captured onto a computer and a three dimensional model of the prostate gland constructed.
A template is mounted against the perineal skin. Through this template needles will be inserted into the prostate gland.
A plan is created to place seeds into the prostate gland according to the size and shape of the gland.
Needles are inserted into the prostate gland through the template.
The prostate being rubbery and mobile alters shape and position. How much it changes varies from patient to patient.The original plan is modified for the new shape and the seeds are then inserted.
The prostate is checked after seed placement for any cold spots. If present they are implanted with additional seeds. The procedure is then complete.
After waking up, the patient has a CAT scan of the prostate gland and the catheter is removed. After passing urine the patient is discharged.