What are the different types of brachytherapy (IRT – Internal Radiation Therapy)?
“Internal” radiation or brachytherapy involves use of a variety of radioactive isotopes which are placed inside or near the tumor/cancer. By doing so, radiation does not have to go through the normal tissue between an external source and the target of radiation. Depending on whether the radioactive isotope is placed permanently or used temporarily, brachytherapy is categorized into two categories of permanent and temporary.
The most common form of permanent brachytherapy is prostate seed implant. In this form of treatment either Palladium (Pd-103) or Iodine (I-125) seeds are implanted inside the prostate. These seeds would irradiate the prostate gland and the cancer inside it as long as they are radioactive but eventually become inert.
Depending on the strength and therefore speed of delivery of radiation, temporary brachytherapy is categorized into Low Dose Rate and High Dose Rate brachytherapy. The most common example of temporary brachytherapy is the use of either Low Dose Rate (LDR) or High Dose Rate (HDR) forms of brachytherapy for the treatment of gynecological cancers specifically cervical and endometrial cancer. Through special catheters either cesium-137 (LDR) or iridium-192 (HDR) would be inserted nearby the tumor. During the period of time when the catheters remain in area, the prescribed dose of radiation would be delivered to the target. This would take about 48 hours in LDR but only a few minutes in HDR treatment.
HDR brachytherapy is also used in the treatment of breast cancer. This form of radiation for breast cancer is called Accelerated Partial Breast Irradiation or APBI. After a lumpectomy a special applicator such as Mammosite or Contura balloon catheter or a Savi applicator is placed inside the lumpectomy cavity. Using HDR technology an iridium-192 radioactive source is inserted into any of these catheters to deliver radiation to the wall of the lumpectomy cavity.
Intraluminal brachytherapy is also used for the treatment of endobronchial tumors, esophageal cancer and cancers of biliary tract. Other forms of temporary brachytherapy include radioactive eye plaque in treatment of choroidal melanoma and Strontium-90 applicators for treatment of pterygium.