Treatment Options: Brachytherapy
High Dose Rate Brachytherapy
High Dose Rate (HDR) brachytherapy is a form of internal radiation therapy which is used in combination with external beam radiotherapy. It is typically used to treat intermediate and high risk prostate cancers. At this point in time HDR Brachytherapy is used in combination with external beam radiotherapy, and not as a stand alone treatment like seed brachytherapy.
The treatment is delivered through the use of small plastic catheters inserted directly into the prostate gland. These plastic catheters act as a conduit allowing a radiation source to be placed within the prostate. A number of radiation treatments can then be delivered through these catheters. Once the radiation has been delivered the catheters are removed and no radioactive material is left within the prostate gland. A computer controlled device, called a Remote Afterloader, moves a radioactive iridium source, located on the end of a wire, into each of the catheters. The radioactive iridium source is then positioned at a number of “dwell” positions to deliver the radiation dose within the prostate. These positions are determined with the aid of a planning computer allowing optimal dose of radiation to the prostate. The treatment is tailored to deliver an optimal dose to the prostate and to minimise the dose to other structures, including the urethra and the rectum. The ability to alter the dose after the plastic catheters have been inserted into the prostate is one of the major advantages of HDR brachytherapy.
HDR brachytherapy involves a treatment program, which comprises three separate stages:
- Short or long term hormonal therapy;
- High dose rate brachytherapy and
- A moderate dose of external beam radiation.
This treatment approach aims at optimising cancer control within various regions. The hormonal therapy acts systemically as well enhancing the effects of the radiation within the prostate. External beam radiation is used to treat potential prostate cancer that has spread beyond the capsule of the prostate and in the surrounding tissues and lymph glands. The HDR component of the treatment aims at maximising the dose of the radiation, or dose-escalating, where there is the highest likelihood of cancer, that is, within the prostate.
Implant Procedure
Typically the patient is admitted the day of the surgery. A bowel preparation kit is provided and there is a regime of medications to be taken in the lead up to the HDR implant.
The HDR implant involves a short procedure in the operating theatre where small hollow plastic needles (HDR catheters) are placed into the prostate through the skin between the scrotum and the rectum.
X-rays and ultrasound imaging ensure that the needles are placed into the optimal position. This procedure is done under a general anaesthetic or spinal anaesthesia.
The patient is then transferred to a CT scan where imaging of the prostate and catheters is undertaken. Computer planning allows accurate calculation of the dose to be delivered and adjustment of the radioactive source positions within the prostate. Once the plan has been completed, the radioactive iridium source is delivered to the prostate. Three separate treatments are then delivered over 36 hours.
The period of hospitalisation is typically 2 days. The needle placement is performed in the morning, a CT scan is performed by midday and the planning is completed in the early afternoon. The first treatment of HDR is delivered late in the afternoon of the first day. The following day a treatment is delivered in the morning and again in the afternoon. Once the treatment has been delivered the catheters can be removed and patient discharged the following morning. During the 2 days the patient is confined to bed and significant movement, such as sitting up or walking, is not possible. A urinary catheter is inserted during the initial procedure and removed at the end of the brachytherapy treatment.
External Beam Radiation
Approximately 2-3 weeks after the completion of the HDR Brachytherapy a course of external beam radiation treatment is delivered. This is at a moderate dose (46Gy in 23 separate treatment sessions) over 4-5 weeks. Each session is given as an outpatient and usually takes 20-30 minutes. A planning session, or simulation, will be required to plan this part of your treatment. The extent of the radiation field is determined primarily by the potential risk of the cancer for spread beyond the capsule of the prostate and to the lymph glands.
Hormonal Therapy
Hormonal therapy is usually commenced at least 3 months prior to the HDR Brachytherapy and continued for a short interval afterwards. Patients with high risk disease may continue with hormonal therapy for longer periods after the HDR Brachytherapy. This will be discussed by a radiation oncologist or urologist.
Side Effects
Slight bleeding and bruising and tenderness between the legs are common. Burning on urination, urinating more frequently, or a feeling of being unable to pass urine freely are possible side effects.
Rectal discomfort is uncommon with respect to the HDR component of the treatment. Towards the end of the external beam radiation treatment some patients may experience temporary diarrhoea. Long term complications from the external beam radiotherapy are uncommon due to the moderate dose which is used. Urinary incontinence is very rare.
The risk of developing impotence is thought to be approximately 30-40%. This is similar to other forms of radiation or brachytherapy. Long term results are not yet available. If impotence occurs it can usually be treated with the use of tablets such as Viagra, or other medications or procedures.
|