High dose rate (HDR) brachytherapy involves the placement of wires into the prostate to deliver high doses of radiation directly into the prostate. Three treatments are given over a 36-hour period and are intended for patients with advanced prostate cancer.
By delivering a higher dose it is more likely to cure more aggressive cancers than conventional radiotherapy. The technique was pioneered here at St Vincent’s
The accuracy of the treatment protects the bowel from being damaged by the radiation and there is a five-fold decrease in damage to the rectum compared to conventional radiotherapy doses.
Combination radiotherapy, HDR is always given in association with around four weeks of external beam radiotherapy. The external beam radiotherapy is generally given two weeks after the completion of the high dose rate brachytherapy.
Major side effects have been uncommon with only a 1% chance of major bowel damage. This treatment serves as an excellent option in locally advanced cancers, which have not spread, to other organs.
International data for this combination treatment resulted in 10-year disease-free survival rates of 80% to 90% — even in men with cancers of an intermediate grade. In more aggressive tumours that may not be amenable to surgery, combination therapy or newer forms of conformal radiotherapy may become the standard of care.
Low dose rate brachytherapy, commonly known as SEEDS, involves the implantation of radioactive pellets or seeds into the prostate. Depending on the size of the prostate between 75 and 100 seeds are used.
The technique is only suitable for patients who have a low risk cancer and a small prostate, as well as minimal urinary symptoms. The ideal patient is a man over 60 years of age who wishes to minimise the side effects of therapy.
Once it has been established that a patient is potentially suitable for brachytherapy, a volume assessment is performed. This involves an ultrasound, which is achieved under a light anesthetic, and an examination of the bladder takes place at the same time. This template tells me the patient’s suitability for brachytherapy and also can be used to plan the accurate placement of seeds.
A computer plan of where the seeds are to be placed is then generated. There is usually a two to three week time lag from the volume assessment to the actual placement of seeds, which are sourced from America.
The patient is assessed by one of the radiation oncologists prior to the therapy. This procedure is performed in the Day Surgery Unit, which is conveniently located on level three at St Vincent’s Clinic.
Advantages of SEEDS
The great advantages of low dose rate brachytherapy are its single-session and outpatient nature. The 10 year survival rate for low risk cancers is identical to surgery. Side effects are minimal, with incontinence and rectal damage rare. Impotence may occur in 50% of patients, but it is generally less severe than that occurring after surgery and responds well to Sildenafil.
Urinary frequency is common for the first one to 12 months and a very small minority has difficulty passing urine. Erectile dysfunction was previously believed to be less common with this technique than any other treatment for localised prostate cancer, however more recently this has not been the case. If erectile dysfunction does occur, it is always less severe than post-surgical erectile dysfunction.