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Newer forms of radiation treatment work to escalate tumor dose and minimize toxicity to healthy surrounding tissue. Advanced radiotherapy techniques include three-dimensional conformal radiotherapy (3D-CRT), intensity modulated beam radiation therapy (IMRT), image-guided radiation therapy (IGRT), intra-operative radiation therapy (IORT), proton beam radiation therapy (PBRT), tomotherapy, systemic radiation therapy, radioimmunotherapy (RIT), and hypofractionated radiation therapy.
What is Radiation Therapy
for Prostate Cancer?
There are three ways radiation may be delivered to prostate cancer patients: by a machine outside the body (external beam radiation therapy), by placing radioactive materials inside the body (internal radiation therapy or brachytherapy), and by ingesting radioactive substances (systemic radiation therapy). External therapy has been in practice longer than brachytherapy. This treatment is often referred to as radiotherapy. EBRT has been so commonly used that EBRT and radiation therapy are sometimes used interchangeably.
The goal of treatment is to irradiate a targeted area with as much energy as possible while avoiding the neighboring organs. Newer versions of external therapy include 3D-CRT, IMRT, IGRT, IORT, PBRT, and hypofractionated radiation. Proton beam therapy is becoming a more widely accepted treatment for prostate cancer, while neutron beam therapy is still in the experimental stages.
Why does Radiation Therapy Work for Prostate Cancer?
Radiation is used as a prostate cancer treatment because high energy waves damage the DNA of cells. If a cell divides prior to repairing the damage, the cell will die. Since cancerous cells divide more rapidly than healthy cells, carefully aimed energy will cause their destruction.
Generally, prostate cancer radiation is administered in daily treatment sessions over a period of five to nine weeks. During this process, the healthy cells that are repeatedly exposed will be unable to repair the extensive damage. Therefore, the precise aiming of the beam or the delivery of the proper radiation dose is crucial to the success of the treatment and the avoidance of side effects.
How do these radiation treatments differ from one another?
Prostate cancer radiation treatment can be divided into categories based on the high-energy wave they use. Most types of external beam radiation therapy use accelerated subatomic particles called electrons to generate waves of high energy photon radiation. Proton beams use a subatomic particle called protons. Neutron beam therapy uses the subatomic particles called neutrons.
The History of Radiation Therapy
Prostate cancer radiation treatment has been used in the United States since 1915. The first radiotherapy used radium applicators positioned adjacent to the prostate gland; unfortunately, this technique resulted in significant morbidity. The next technique in radiotherapy used electron beam x-rays; however, these x-rays could not penetrate deeply enough to irradiate the affected tissue. The x-rays were used mainly for palliative care because they also caused skin cancer.
After World War II, doctors were able to use megavoltage in prostate cancer treatment. They used radioactive isotopes from Cobalt 60. By the 1980s, radiation oncologists began using the linear accelerator which increased the speed of particles and allowed for the most precise aiming of the beam.
Fractionated Prostate Cancer Radiation Treatment
External beam radiation is sometimes called fractionated, meaning that doses of radiation are given over a period of time, which is typically once daily – Monday through Friday – for five to nine weeks. Hypofractionated radiation therapy delivers higher doses of radiation to targeted areas in fewer radiation treatment sessions. Hyperfractionated radiation therapy delivers lower doses of radiation to targeted areas more than once a day. A patient may undergo fractionated, hypofractionated, or hyperfractionated radiation therapy based on their specific condition.
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