LDR brachytherapy: Past, present & future
Prostate brachytherapy is a targeted form of internal radiotherapy (sometimes referred to as low dose-rate or LDR brachytherapy). It is targeted only at the site of the tumour so the radiation kills the cancer cells without causing major damage to surrounding healthy cells. Tiny seeds containing the radiation are passed through fine needles and positioned directly into the prostate gland. It is not major surgery and usually patients will only spend 1 day in hospital. Most men return to their usual pre-treatment activities within a couple of days.
A brief history of brachytherapy
The term ‘brachytherapy’ derives from the Greek word for ‘short’, brachy, referring to the distance between the therapeutic agent and the target lesion.
Alexander Graham Bell was the first to describe the idea of putting radioactive sources in the prostate. In a letter dating back to the 1890’s he discussed placing radium inside a glass bead and inserting it inside the prostate. However, the first actual procedures using a primitive technique, which consisted of placing non-sealed sources of radioactive gold into the prostate, were reported in 1913.
The field was significantly advanced in the early 1970’s when a technique was developed for implanting the prostate with radioactive isotopes using permanent sealed sources. Using a surgical approach, they exposed the prostate gland and prepared it for seed implantation. The prostate volume was determined in the operating room and the total dose of iodine required for the implant was obtained from a nomogram, specifically developed for this technique. Needles were then inserted into the prostate with a freehand technique. This technique was performed for over 15 years with encouraging early results.
Subsequent emerging failures were put down to the inaccuracies of the manual measurements used throughout the procedures and by the mid-1980s this type of open implant was abandoned.
The “modern” era of prostate brachytherapy evolved from Denmark where they began to use ultrasounds to help plan seed placement and continuing advances in technology were used to further improve the process. In the operating room physicians could follow the computer generated plan by attempting to guide the needles with the seeds into predetermined coordinates. Seeds can now be inserted by a number of techniques: the needles can be loaded with loose seeds before the implant (pre-loaded needles) or during the implant (Mick applicator-based technique). An alternative to loose seeds is using seeds woven in polyglycolic strands.
LDR brachytherapy today
Today, a patient referred for LDR brachytherapy will first attend an appointment with the Oncologist for treatment planning. During planning, ultrasound scans of the prostate allow the clinicians to plan the appropriate radiation dose. Modern day imaging and biopsy techniques especially with MRI imaging are enabling clinicians to map the exact location of the tumour.
At the time of the procedure, the patient will have a general or epidural anaesthetic. The radioactive seeds are inserted into the prostate using hollow needles that allow accurate positioning according to the plan. Ultrasound is usually used to guide the needles to deliver the seeds through the perineum. After they have delivered the seeds, the needles are then removed.
Following the procedure, the seeds remain in place over a period of months, emitting very low doses of radiation until they become inactive. This approach destroys the tumour with minimum damage to the surrounding healthy tissue and in a way which is least disruptive to ‘normal’ life.
Today it is widely accepted that LDR brachytherapy is successful in treating low risk patients. A recent randomized clinical trial (known as the ASCENDE-RT study) shows bio-chemical disease free survival rates improve by 50% over an average of 6 to 9 years, with intermediate or high risk Prostate Cancer patients receiving LDR brachytherapy) This success rate, together with few side effects and minimal disruption to normal life, makes LDR brachytherapy a favourable option.
The future of LDR brachytherapy
A new and innovative method becoming more available in a number of hospitals is 4D Brachytherapy. It requires just an initial outpatient assessment, followed by the seed implantation, during which the planning is performed in real-time. 4D Brachytherapy uses a combination of pre-loaded stranded seeds around the periphery of the prostate gland and seeds optimally placed within the centre. From a simple clinic-based scan, a web-based nomogram allows the calculation of the number of stranded and central seeds required for the procedure. The whole procedure can be done more efficiently and accurately in under an hour, with a quicker recovery time and with fewer side effects for the patient.
Improved dosimetry (the calculation and assessment of the radiation dose received by the human body) and positive clinical outcomes of 4D Brachytherapy, together with reduced side effects, have been demonstrated over the traditional brachytherapy approaches.