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Glossary
Radiation Therapy
Radiation therapy uses high-energy x-rays, either beamed from
a machine or emitted by radioactive seeds implanted in the
prostate, to kill cancer cells. When prostate cancer is
localized, radiation therapy serves as an alternative to
surgery. External beam radiation therapy is also commonly
used to treat men with regional disease, whose cancers have
spread too widely in the pelvis to be removed surgically, but
who have no evidence of spreading to the lymph nodes. In men
with advanced disease, radiation therapy can help to shrink
tumors and relieve pain.
External Beam Radiation Therapy
External beam radiation therapy generally involves treatments
5 days a week for 6 or 7 weeks. The treatments cause no
pain, and each session lasts just a few minutes. In many
cases, if the tumor is large, hormonal therapy may be started
at the time of radiation therapy and continued for several
years. The primary target is the prostate gland itself. In
addition, the seminal vesicles may be irradiated (since they
are a relatively common site of cancer spread). Radiating the
lymph nodes in the pelvis, once common practice, has not
proven to produce any long-term benefits for most patients,
but it may be necessary in certain circumstances.
Internal Radiation Therapy
Radiation can also be delivered to the prostate from dozens
of tiny radioactive seeds implanted directly into the
prostate gland. This approach, known as interstitial
implantation or brachytherapy, has the advantage of
delivering a high dose of radiation to tissues in the
immediate area, while minimizing damage to healthy tissues
such as the rectum and bladder.
As practiced today, internal radiation therapy relies on
ultrasound or CT to guide the placement of thin-walled
needles through the skin of the perineum. Seeds made of
radioactive palladium or iodine are delivered through the
needles into the prostate, according to a customized
pattern—using sophisticated computer programs—to conform to
the shape and size of each man's prostate.
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