Brachytherapy for Prostate Cancer

What is Brachytherapy?

Brachytherapy is radiation therapy where the source of radiation is placed close to the tumor inside the body.  It differs from external beam radiation therapy because instead of the radiation coming from outside the patient the radiation source is implanted inside the body permanently or temporarily.

There are two types of brachytherapy procedures for prostate cancer:

Prostate Seed Implants

The first type is where radioactive seeds are implanted permanently inside the patient.  Small radioactive seeds which  are about the size of a grain of rice each are implanted with needles through the patients perineum and into and around the prostate.  These seeds are made of radioactive material such as iodine-125 or palladium-103.   Typically around 80 - 100 of these small seeds are placed in a pattern in the prostate.  This procedure takes about 1 hour and is done while the patient is under general anesthesia.  The seeds will be implanted in the proper pattern that is determined by the physician and a team of physicist to give the optimal distribution of radiation to the tumor.

Since the radioactive seeds are placed in such a close proximity to the tumor they will deposit their dose directly into the tumor while sparing the surrounding tissue from recieving little if any of the radiation.  This cuts down on the side effects of the radiation substantially.  If the radiation was to be given by external beam radiation therapy the radiation would have to enter the body from the outside to get to the tumor.  Since the radiation with external beam must enter from the outside it will pass through normal and healthy tissue to get to the tumor located in the prostate.  This irradiation of normal tissue such as the bladder and rectum will cause temporary side effects.  With the seed implants the radiation is placed in direct contact with the tumor from the inside so very little normal tissue will be affected.

The seeds will be permanent but they will not always emit noticeable doses of radiation.  One the seeds reach their half life their radioactivity is half of what it was when they where first implanted.  Usually after 7 half lives a material is considered non-radioactive. Iodine-125 has a half life of around 60 days and Palladium-103 has a half life of 17 days. After the procedure the radiation oncologist will tell you not to go around small children or pregnent woman for a specified period of time.  This is because the seeds are still working and emitting radiation.  Once the doctor says it is safe to be around young growing children and pregnant woman it is safe. Usually the time period is around 3 - 6 months but this is dependent on the type of seeds you  get.

HDR Brachtherapy

The second type of brachtherapy procedure used for prostate cancer involves the use of high dose rate or HDR radioactive sources.  The HDR procedure is usually done after 5 weeks of external beam radiation therapy and is used in high risk prostate cancers.  After the initial 5 weeks of external beam radiation the patient will be given 1 to 3 HDR sessions. 

The HDR treatment is given under general anesthesia and several needles will temporarily be placed inside the prostate.  The needles are then attached to the HDR machine which will then push the radioactive sources through the needles to the prostate.  While the sources are in the needles they move to different positions around the prostate depositing their dose of radiation.  Once this procedure is over the sources are removed back into the HDR machine and then the needles are taken out.  No permanent sources or seeds are left in the patient after this type of brachytherapy treatment and once the procedure is over the patient will not be "hot" (radioactive).