Radiation Therapy for Prostate Cancer
Two types of radiation therapy are used to treat prostate cancer: brachytherapy and external radiation therapy (XRT).
This treatment involves implanting tiny, radioactive capsules (called "seeds") into the cancerous prostate gland. The seeds emit radiation that kills the malignant tumor. Men with small tumors confined to the prostate (stage T1 or T2) are candidates for brachytherapy.
Transrectal ultrasound (TRUS) is used to create a three-dimensional grid map of the prostate, and a computer calculates the volume of the gland, the number of seeds needed, and determines where they will be placed.
The procedure is performed on an outpatient basis and takes 45 to 60 minutes. The patient is given regional anesthesia. A needle is inserted through the perineum and into the predetermined site(s). Fifty to 100 rice-sized seeds are implanted into the prostate through the needle. The seeds contain a radioactive isotope (usually palladium 103 or iodine 125) that emits radiation for about 3 months and then becomes inert.
Brachytherapy patients are discharged the same day and usually resume routine activity within a day or so. A recent study has shown that most brachytherapy patients remain free of prostate cancer 5 years after treatment.
A small number of patientsgenerally over age 70experience incontinence or impotence (erectile dysfunction, ED).
External Radiation Treatment (XRT)
XRT is recommended when the tumor has spread through the prostate capsule to surrounding tissues. XRT usually is given on an outpatient basis for 7 or 8 weeks. High-energy x-rays are projected onto prostate tissue from a machine outside the body. The radiation destroys cancer cells and shrinks tumors.
A study of 999 patients found 79 percent of stage T1, 66 percent of stage T2, 55 percent of stage T3, and 22 percent of stage T4 prostate cancer patients survived 10 years after XRT.
Recently, CyberKnife stereotactic radiosurgery is being used in some treatment centers to treat prostate cancer. In this procedure, a computer program is used to determine the precise shape, size, and location of the tumor, and a robotic arm helps deliver highly concentrated beams of radiation from many different angles and positions. These beams intersect at the tumor and thus, should not damage healthy tissue.
Erectile dysfunction (i.e., impotence, particularly in older men), discomfort with urination, urinary urgency, and diarrhea (especially during the late stages of treatment) are commonly experienced with XRT.