What is Brachytherapy?
Brachytherapy derived from the Greek word ‘brachy/os’ meaning ‘close to’. By placing radioactive seeds within the prostate gland/cancer, it is possible to deliver a huge ablative or curative dose of radiotherapy to a cancer (higher than by usual external beam conformal or IMRT radiotherapy), whilst minimising the dose to the rest of the pelvic organs due to the ‘inverse square law’. The inverse square law is a physics’ which states that: ‘the intensity of radiation falls off at the square of the distance from the source of the radiation’
How does it work?
Radiation, sometimes referred to as ionising radiation, is emitted by the iodine-125 seeds (one of the isotopes used in the treatment of brachytherapy )and causes damage to the DNA of the cells in the prostate gland. This results in the breakdown of the DNA and, unless repair occurs, this damage will result in the death of the cells. Cancerous cells are less able to repair themselves and so are more likely to be killed by the radiation dose. While some normal cells will be affected, and some killed, the majority is left undamaged.
Over the last decade, very precise methods of prostate imaging have been perfected, allowing the very exact volume definition and preplanned distribution of seeds within any individual’s prostate. This, plus the technical advances in three dimensional delivery of seeds to pre-mapped locations within the prostate has allowed designer implants of prostate cancer with radioactive seeds that are ‘bespoke’ for each individual’s case with regard to size, shape and cancerous distribution within the gland.
The radioactive seeds used for implant brachytherapy are 125-iodine; they employ photon emissions to deliver the radiotherapy. The radioactivity has a 60 day half-life. the seeds remain in permanently. Although other radioactive isodose have been used and other techniques also, the Seattle method is the best validated in the world, with by far the largest follow-up to base comparisons with surgery – against which the technique is comparable in terms of cure rates.
If you have any questions that are not answered here, please contact the Brachytherapy Co-ordinator at the Princess Grace Hospital on 020 7486 1234 - Bleep 53
