Brachytherapy is a medical procedure used primarily in cancer treatment. The procedure involves inserting radioactive material in the form of tiny "seeds" into or near a tumor or other area of concern. Brachytherapy allows physicians to target a cancerous tumor directly with a high dose of radiation without exposing surrounding healthy tissue to dangerous levels of radiation. Brachytherapy has been used to treat cancer for more than 100 years. Over the past few decades, improved technology has made the procedure safer and the outcomes much more predictable. Some large medical centers perform hundreds of brachytherapy procedures a year.
Procedures
Medical experts including oncologists, radiation oncologists, medical physicists and dosemitrists typically work as a team to determine the precise brachytherapy treatment dosage, placement of the seeds and duration of the implant. After initial ultrasound imaging of the tumor area, treatment is planned using computerized modeling. The brachytherapy procedure is done in conjunction with ultrasound. "Seeds or pellets resembling a small clicker on a ballpoint pen are placed using needles or hollow tubes about as big as a stick of incense, but more pliable," explains Kristofer Kainz, Ph.D., a medical radiation physicist with the Wisconsin Medical College's department of radiation oncology. In targeting a tumor, 70 to more than 100 seeds might be placed, depending on the turmor's size, Kainz said.
Diseases Treated
Brachytherapy is used in the treatment of many cancers, including prostate, cervical, breast, lung, bile duct, soft tissue sarcomas, esophageal, endometrial and ocular melanoma, and certain cancers of the head and neck. Brachytherapy is also sometimes used to treat nonmalignant conditions, such as when a stent is implanted during heart surgery. Brachytherapy implants are inserted to prevent scarring around the stent.
Seed Types
Several types of seeds are used in brachytherapy. Palladium seeds are sometimes used for aggressive, fast-growing tumors because palladium produces radiation more quickly and over a shorter time period. Iodine seeds are usually used to treat slow-growing tumors. Echogenic seeds, those that emit a high frequency that can be observed in ultrasound images, aid the physician in placing the seeds in the target area.
Low-dose Rate Implants
With low-dose brachytherapy, generally used in nonaggressive, slow-growing tumors, the radiation is inserted and kept in place between one and seven days. Patients generally remain in the hospital, according to the National Cancer Institute. Once the treatment time is over, the radiation sources and catheter are removed.
High-dose Rate Implants
In brachytherapy with high-dose rate implants, the radiation seeds are placed for 10- to 20-minute sessions, then removed. Depending on the type of cancer, patients might receive treatments twice a day for several days, or undergo one treatment a week for up to five weeks. Sometimes, patients are permitted to leave the hospital and return daily for treatments. As with low-dose implants, the catheter or applicator is removed after treatments are completed.
Permanent Implants
Often when aggressive tumors are present, seeds are implanted and left in the body to decay over time. For example, the radiation used to treat prostate cancer is delivered during the first half-life of the isotope. For iodine-125, the common radioactive source used for prostate cancer, the half-life is 60 days, according to the American Brachytherapy Society. The seeds emit low levels of radioactivity just millimeters around the area where they are implanted. After the seeds are placed, the catheter is removed. Some patients receive permanent brachytherapy implants in combination with other radiotherapy as part of their cancer treatment.
Safety and Side Effects
Because the seeds are tiny---about the size of a grain of rice or a sesame seed--- they cause little discomfort. The procedure is performed under general or spinal anesthesia. Possible side effects after prostate and cervical brachytherapy treatment include frequent urges to urinate, impotence in men, and discomfort or bleeding in the rectum. Continuing improvements in technique and precision have lessened the chance of side effects. Experts recommend that patients receiving brachytherapy avoid close contact with children and pregnant women for a few days after the procedure, because there is a slight risk of exposure to the radiation.
References
- American Brachytherapy Society: A Brief History of Brachytherapy
- Interview: Kristofer Kainz, Ph.D., Department of Radiation Oncology, Wisconsin Medical College
- MayoClinic.org: Brachytherapy
- National Cancer Institute: What to Know About Brachytherapy
- Memorial Sloan-Kettering Cancer Center: Radiation Therapy
