Brachytherapy may be used exclusively (monotherapy) or in conjunction with other treatments such as external radiotherapy or hormone therapy. Until the mid-1980s, the method for the treatment of prostate cancer with brachytherapy used permanent implants.
In 1992, the system of high dose-rate (HDR) brachytherapy came into use.
The following is a description of both types of prostate brachytherapy, offering the most suitable and effective treatment to each individual patient.
HDR Brachytherapy for Prostate Cancer
HDR (High Dose Rate) brachytherapy is usually used in combination with external conformal radiotherapy and/or hormone therapy. It may also be used as rescue treatment for cases where the tumor has relapsed after radical prostatectomy, external beam radiotherapy or seed implant. HDR brachytherapy as an overdose after external radiotherapy is recommended in male patients who:
- is in any stage of the localized disease, Stages T1-T3b
- present extra-capsular extension or involvement of the seminal vesicles
- have any PSA value without evidence of metastatic disease
- have any degree of Gleason score
- present perineural invasion evidenced by CT, MRI or biopsy
- have had previously undergone a transurethral resection (TUR)
- present any size of prostate
- have or have not previously received radiotherapy treatment to the prostate
- have been previously treated by external radiotherapy and/or permanent implants and currently have a recurrent disease (local failures).
- present local recurrences after radical prostatectomy
Protocol for Monotherapy with HDR Brachytherapy.
In some special cases, high dose-rate brachytherapy may also be used as a single treatment, without external radiotherapy or hormone therapy.
These cases are also candidates for seed brachytherapy, but as they have undergone previous transurethral resection it is not recommendable.
If a permanent implant of Iodine 125 seeds can successfully be used as monotreatment, HDR brachytherapy implants can also be used with success, without any need for other complementary treatments.
A selected group of patients are candidates for treatment under the HDR Monotherapy protocol.
As can be seen, patients who have undergone previous TUR (transurethral resection) are NOT excluded. The High Dose Rate (HDR) brachytherapy procedure consists of 1 implant that supplies the dose in 4 fractions.
Procedure for HDR (High Dose Rate) Brachytherapy .
The physician reviews the patient’s record and the last analysis and then determines the type of treatment to be applied. This is done during the first visit. If necessary, a preoperative workup (full blood panel with coagulation tests, chest X-ray and ECG) and an extension study are then requested, which should be brought to the following visit when the patient is given an appointment for the implant.
On the day of the implant an epidural anaesthesia is applied. The patient is placed in a treatment position that enables the physician to have easy access to the perineum. The application involves the use of a guide support and flexible treatment catheters.
Under real-time sonographic control, the prostate and its limits are defined and a suitably sized support is placed in the perineum in a position to suitably cover the whole prostate. The support is held in place by hand while the flexible tubes are inserted, so that the physician has greater control over the placement of the tubes, angling them and directing them towards the prostate. Using a suitably sized support and guiding the placement of the guide tubes under sonographic control,, the physician can properly treat any size of prostate, perineural or extracapsular extension or seminal vesicle invasion there may be. The HDR implant’s enormous capacity for adaptation makes it possible to treat even very large prostates without having to increase the number of needles inserted. The pubic arch sometimes interferes with the placement of rigid needles, but with the use of flexible guide tubes the pubis is no longer a problem.
When the flexible tubes are in position, the support is sutured to the perineum to stabilise the implant. A radiopaque catheter is placed in the bladder to simplify urine drainage and show the urethra in x-ray images. A catheter is also usually inserted in the rectum to administer radiopaque contrast to be able to identify it on an X-ray. Once the patient has recovered from the spinal anaesthesia, they are moved to the simulation room for a CT scan.
After obtaining the images, the patient waits in a room in our centre until the treatment plan has been processed by specialised computers, called planners. The parameters of the treatment unit are calculated so that the prostate receives an adequate dose while minimising the dose received by the urethra, rectum and bladder.
When the physicist and the physician have approved the treatment plan, the patient is transferred to the treatment room, where the catheters are connected to the irradiation unit. Before performing the treatment, the system verifies that all the tubes are correctly connected and that treatment can be applied without any inconveniences. As of this moment the patient is alone in the treatment room, but is constantly monitored through closed circuit television and an intercom.
The patient feels no pain or discomfort. Generally, “clicks” are heard as the source progresses through each of the guide tubes. Average treatment time is 10 to 20 minutes. After treatment, the source is returned to storage. The patient is not radioactive at any time and is returned to the room and a few hours later, the second treatment is performed.
This second treatment requires much less time because the simulation and planning do not have to be repeated. After the second treatment (or third, if the patient receives HDR monotherapy) the catheters and support are removed. This does not require anaesthesia. After withdrawal of the flexible needles, gauzes are used to apply a light pressure to the perineum to prevent the formation of haematomas. The patient returns to the room, where they are monitored to ensure they feel well, before being discharged to their home.
Whenever necessary, the second implant is performed one week later, following the same procedure as described above.
CT-based 3D dosimetry.
This imaging technique is used to evaluate the implant using CT-based 3D scan images. The image shows the implant in 3D. It can be rotated to see the radiation coverage of the prostate and the proximity to other structures, such as the rectum.
Dose distribution of HDR implants
This is a cross-sectional view of a prostate implant carried out in the IMOR Institute showing the radiation isodoses.
It shows the central area of dose reduction, produced in the physics unit, to reduce the dose received by the urethra. The red line visible around the implant is the isodose of the prescribed dose. In its natural position, the prostate comes up against the rectal wall, separated by a thin membrane called a fascia. By using a fixed support, when the physician introduces the flexible needles, he or she raises the prostate at the same time, separating it from the rectal wall to significantly reduce the dose received by the rectum.
With the high dose-rate system, the prostate is held in position throughout the treatment by the catheters, and the catheters maintain their position thanks to the fixation plate. If the patient moves, the implant moves as well. HDR brachytherapy is one of the most precise methods for administrating radiotherapy currently available.
Permanent seed implant prostate brachytherapy
Permanent seed implants are a form of low dose-rate interstitial brachytherapy. The isotope used is Iodine-125. These small seeds (1mm x 5mm) are inserted in the prostate, where they remain while radioactively decaying.
Permanent seed implants are used as monotherapy in cases of prostate tumours with a high probability of being limited to the prostate, without any need to combine it with external radiotherapy or hormone therapy. Permanent implants are ideal in these cases as they are inserted in a day-hospital environment, the patient being discharged within a few hours after the implant is performed. The criteria for applying permanent seed implants are:
- Stage T1-T2b
- Prostate volume < 60 cc
- PSA<=10
- Gleason <= 6
- No significant obstructive symptoms
- No perineural extension
- No previous transurethral resection (TUR)
Permanent seed implant brachytherapy procedure.
At the first visit, the patient’s record is reviewed and the IMOR Institute physician determines the type of treatment to be applied, informing that patient about its characteristics. If necessary, a preoperative workup is requested (full blood panel, with coagulation tests, ionogram, chest X-ray and ECG) which should be brought to the next visit.
At the time of the implant and once under epidural anaesthesia, the patient is placed in the treatment position. The guide plate for the needles is placed on the perineum, the area between the scrotum and the anus. A transrectal ultrasound scan is performed in the treatment position to determine the shape, position and size of the prostate. The prostate image is electronically digitised and transferred to the planning computer, where it is superimposed on a calibrated grid. The physicist makes exhaustive calculations to determine the position to be occupied by each of the seeds and their coordinates, to administer a suitable dose to the entire prostate, protecting the urethra and rectum. The result is a map of the prostate and a list of the coordinates for the brachytherapy needles and the number of seeds in each one. The physician introduces the guide needles through the holes in the guide plate, which has been previously selected by the planning computer, one by one through the perineum until reaching the prostate, guided by sonographic images. When each needle is in position, the seeds are introduced according to the planning indications. The number of seeds placed is variable, but usually between 50 and 100, depending on the size of the gland.
A three-dimensional view of the dose distribution shows that the reference isodose adequately covers the entire prostate. If there is any area with low coverage, additional seeds may be placed nearby to ensure the entire prostate is correctly treated.
Final Considerations.
Brachytherapy is a very effective and well-tolerated treatment.
Current experience shows that its long-term results are at least the same as those obtained with radical surgery, but with the enormous difference of the resultant quality of life after treatment. The side effects of brachytherapy are minimal and above all transitory, being completely resolved a few weeks after treatment.
The IMOR Medical Institute for Radiation Oncology, is a pioneer in the technique of prostate brachytherapy. It has the most advanced technical means to perform the technique most suited to each case.
The highly qualified staff are available at all times, offering personalised attention and the highest quality care.