Radiation for Prostate Cancer
Radiation treatment for prostate cancer uses high-energy rays or particles to kill or slow the growth of cancer cells. Radiation is sometimes used as an initial treatment for those tumors which are small or when the cancer has only partially spread to tissues near the prostate gland. Radiation treatment is also used after surgery to make sure that any remaining cancer cells are destroyed and to make sure that the cancer has a very low chance of recurring.
There are two main types of radiation treatment: external beam radiation and brachytherapy. Brachytherapy is generally only used if the patient has early stage prostate cancer (stage T1 or stage T2).
External beam radiation therapy (EBRT) uses a linear accelerator to focus x-rays on the affected area. After the area has been located by use of x-rays, CAT, or MRI scans, a doctor or nurse makes marks on the patient’s skin to indicate the area to be irradiated. The EBRT is usually given 5 days per week over a period of seven to nine weeks. This treatment lasts only a few minutes and is pain-free. This treatment can be used for all stages of cancer, although in the T4 stage, where cancer has spread far beyond the prostate gland, the treatment is used to relieve pain but cannot completely eradicate the cancer. There are many side effects that may occur with this kind of treatment, such as diarrhea, bloody stool, rectal leakage and large intestine irritation. Other side effects include urinary problems like a burning sensation during urination and the need to urinate more frequently. There is also the possibility of impotence, fatigue and lymphedema.
There are three other forms of external radiation therapy that are now in use. They are three-dimensional conformal radiation therapy (3D-CRT), intensity modulated radiation therapy (IMRT), and conformal proton beam radiation therapy. These forms of therapy are considered somewhat better than standard EBRT because there are fewer side effects, but they have the same benefits.
3D-CRT uses special computer programs to precisely locate the prostate gland in the patient’s body, then uses the information to pinpoint three beams exactly on the spot requiring radiation. The patient is kept immobile with a specially made plastic body cast. The three beams are aimed at the prostate from different directions so that only the prostate receives the full dose of radiation while other tissues along the line of the beams receive only one third of the radiation. This therapy is considered to be as effective as standard EBRT treatment on the cancer cells, but is less damaging to the other tissues in the area.
IMRT is like 3D-CRT in that it uses several beams to limit exposure to healthy tissues. The innovation of this form of therapy is that the machine delivering the radiation actually moves around the patient’s body as it gives the required dose of radiation. Healthy tissue is damaged even less than in 3D-CRT, because the rays move rapidly through healthy tissue and, at the same time, stay focused on the cancerous tissue.
Conformal proton beam therapy is also related to 3D-CRT, but instead of using x-rays, it uses proton beams. Protons are positive parts of atoms and unlike x-rays, they cause little damage to tissues that they pass through. This is because they only release their energy after traveling a specific distance, whereas normal x-rays release their damaging energy all along the path they are traveling. This therapy is not available everywhere yet, because only a few of the machines have been made.
The form of treatment which is internal rather than external is called brachytherapy Forty to one hundred, tiny radioactive pellets, as small as a grain of rice, are inserted into the patient’s prostate gland and left for some months. The pellets deliver the dose of radiation directly to the prostate and not to surrounding tissue.
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