Brachytherapy for prostate cancer

Brachytherapy is the treatment of prostate cancer by the implantation of radioactive isotope (sealed or encapsulated into ‘seeds’) into the prostate.

This method has reached a very advanced level of sophistication in the last ten years due to improvements in ultrasound imaging of the prostate during the procedure (allowing direct visualisation of the deposition of the seeds) and better computer assisted planning and seed delivery methods.Physics_team_in_theatre

The great attraction of brachytherapy is that it is a single procedure, a small operation, with the patients almost always leaving hospital next day.

Brachytherapy depends on the “inverse square law” of physics; this states that around a source of radiation, the dose ‘falls off’ at the square of the distance. Thus, the tissues within the prostate receive very high (cancerocidal) doses of radiation whilst the organs/tissues around the prostate receive a much lower dose than anticipated by other radiation methods and, because of this, the doctor is able to safely deliver a very high dose to the prostate cancer with low risks to adjacent structures.

The inclusion of patients for brachytherapy is defined by relatively strict criteria.  Usually, we accept those biopsy proven patients with a Gleason score less than 8, a gland of less than 50cc, good urinary flow rates and a PSA of less than 15.

Patients are excluded from brachytherapy as monotherapy if their Gleason grade is > 7, their PSA levels are > than 20 ng/ml or if their clinical stage > T2 (early T3a is accepted).

The Procedure

Sagittal view of the Seattle low dose radiation seed implant technique for prostate cancer with the transrectal probe in situ, and the implant taking place via the transperineal route through a template (seen ‘side-on’ in the main diagram but ‘ en face’ in the ‘bubble’ top right), the depth coordinate being called by the rectal ultrasound probe.

Sagittal view of the Seattle low dose radiation seed implant technique for prostate cancer with the transrectal probe in situ, and the implant taking place via the transperineal route through a template (seen ‘side-on’ in the main diagram but ‘ en face’ in the ‘bubble’ top right), the depth coordinate being called by the rectal ultrasound probe.

The delivery of interstitial brachytherapy is nowadays carried out with great precision, utilising trans-rectal ultrasound to visualise the prostate and allow the radioactive seeds to be placed under direct supervision.

After initial assessment and fulfilling the entry criteria for inclusion in brachytherapy treatment, the patient is usually admitted to hospital for thirty six hours. On the first day, a bowel ‘clear out’ is performed via enemas, in order th

at the transrectal probe has a clear view of the prostate at the operation.

On the next morning, patient is anaesthetised, an ultrasound probe is inserted into the rectum and multiple measurements taken to assess the dimensions and configuration of the prostate and its relationship to other structures, such as the urethra.  A metal grid/template is connected to the transrectal probe and its coordinates (at each axial 0.5cm “slice” of prostate from base to apex) are visualised on the planning screen, superimposed on the ultrasound image at that level.

The information that is obtained at this initial procedure is acquired onto a computer and provides the radiotherapist and planning physicists with details that help them to establish a treatment plan, individualised to produce an ideal ‘bespoke’ plan of therapy for that person .  Interstitial brachytherapy requires the insertion of radioactive seeds of Iodine into the prostate and the positioning of these seeds is worked out from a knowledge of the anatomy of the prostate in each patient and from an understanding of the radiation emission characteristics of the implanted seeds.

The metal grid is set up and secured to the operating table.  Through the grid, needles are inserted through the skin of the perineum into the prostate gland, under direct vision using thtetransrectal probe.

When the positioning of the needles is satisfactory and matches the defined radiotherapy treatment plan, the seeds are deposited.

The time taken for this procedure ranges from 1-2 hours.

The patient is then returned to the anaesthetic recovery room and to the ward with a temporary urinary/bladder catheter in situ. This is removed the next morning, after which the patient is discharged.

In the ward and for the next 3 months (as the half life of the isotope is 2 months) there will be no restriction on visiting, excepting close proximity to pregnant women and infants, as there is no significant radiation risk to the patient’s visitors.

Left panel is a plain pelvis x-ray showing seed distribution at the end of implant. The middle panel shows the axial CT cuts through the prostate at various levels from base to apex demonstrating the deposited seeds around the urethra. The right panel demonstrates the template coordinates, through which holes the needles were inserted to achieve this distribution – the middle two pictures showing these coordinates superimposed on ultrasound pictures.

Left panel is a plain pelvis x-ray showing seed distribution at the end of implant. The middle panel shows the axial CT cuts through the prostate at various levels from base to apex demonstrating the deposited seeds around the urethra. The right panel demonstrates the template coordinates, through which holes the needles were inserted to achieve this distribution – the middle two pictures showing these coordinates superimposed on ultrasound pictures.

Side effects

The most common symptoms after brachytherapy are described as ‘irritative’. Almost all patients find that they  have to pass urine more frequently. A medicine called an alpha blocker is usually prescribed for three months to assist the urinary flow that may be (usually temporarily) less strong.

5% of patients require a catheter to be re-inserted (and more commonly in those with a weak stream prior to the procedure – hence the selection of patients by whether they can produce a reasonable stream prior to the procedure). In a consecutive series of 400 patients implanted by our team, only one individual required a catheter after one month.

Two thirds of men retain their sexual potency (but are not fertile).

We have experienced no cases of urinary incontinence and no major rectal problems (exacerbation of haemorrhoids with bleeding may occur).

Radiation delivery to the prostate may also affect the rectum and, if this occurs, patients may develop proctitis.  The symptoms of proctitis are the frequent need to pass a motion, the feeling that a motion is present in the rectum, and sometimes the passage of bleeding and mucus.  Just like urinary symptoms, proctitis usually resolves, rarely persisting beyond 3 months.

Results

The largest clinical work and the longest follow up of patients treated with iodine-125 seeds (our own method) comes from Seattle and the results are entirely comparable with those of surgery or other radiatiom methods in terms of cure.

Our own data on PSA results following this procedure are shown in the figure below.

Median PSA values in 50 patients treated with brachytherapy by our team

Median PSA values in 50 patients treated with brachytherapy by our team