Brachytherapy is a form of localized radiation therapy involving the direct placement of radioactive material close to or inside a tumor. Brachytherapy varies by dose, mode of delivery and the location of the cancer.
Permanent and temporary brachytherapy
In permanent brachytherapy, seeds containing the radioactive material are implanted either inside or nearby the tumor. Low dose radiation is gradually absorbed over time and eventually fades after six months.
For temporary brachytherapy, a catheter or applicator is used to deliver the radiotherapy to a target site. In cases of low dose therapy, the radioactive material is usually placed in the delivery device for 12 to 24 hours before being removed, while high dose radiation may only be administered for a matter of minutes.
Low or high dose brachytherapy
High dose-rate (HDR) brachytherapy
HDR (>12 Gy/h) brachytherapy is given over periods of 10 to 20 minutes. This is usually performed as an outpatient procedure, although patients are sometimes admitted to hospital for one to two days if they are receiving more than one session of treatment. The radiation dose is delivered as a short burst using a remote afterloading machine.
Low dose-rate (LDR) brachytherapy
LDR (0.4-2 Gy/h) brachytherapy is administered at a continuous rate in sessions that can last up to 50 hours.
Treatment can also be delivered in periodic pulses, referred to as pulsed dose-rate or PDR. Here, the radiation is usually delivered once every hour rather than continuously.
Location of the implant
Some of the places in the body where a brachytherapy implant may be inserted include:
- Intracavitary brachytherapy - The radioactive source is inserted into a body cavity such as the vagina or uterus
- Interstitial brachytherapy - The source is inserted into bodily tissues
- Intraluminal brachytherapy - The source is placed within an intraluminal space such as the esophagus or trachea
- Surface (mould) brachytherapy - Radioactive moulds are attached to the surface of the skin
- Intravascular brachytherapy - The source is placed within blood vessels
Brachytherapy according to source loading
Brachytherapy is delivered to the target site using one of two methods:
- Hot loading - The radioactive material is placed manually and directly into the target tissue.
- Afterloading - A delivery device is placed into position using imaging studies and then loaded with radioactive material either by hand (manual afterloading) or by an automated machine (automatic remote afterloading).