Radiation Therapy
External Beam Radiation Therapy
Proton Therapy
Brachytherapy
Radiation involves the killing of cancer cells and surrounding tissues with directed radioactive exposure. (Review the roles of the prostate and the surrounding organs in the About the Prostate section.)
The use of radiation therapy as an initial treatment for prostate cancer is described below. Some forms of radiation therapy can also be used in men with advanced or recurrent prostate cancer.
External Beam Radiation Therapy
The most common type of radiation therapy is external beam radiotherapy. CT scans and MRIs are used to map out the location of the tumor cells, and x-rays are targeted to those areas. With 3D conformal radiotherapy, a computerized program maps out the exact location of the prostate tumors so that the highest dose of radiation can reach the cancer cells within the gland.
Intensity-modulated radiation therapy (IMRT) allows oncologists to modulate, or change, the intensity of the doses and radiation beams to better target the radiation delivered to the prostate, while at the same time delivering lower doses to the tumor cells that are immediately adjacent to the bladder and rectal tissue.
Because the treatment planning with these types of radiation therapy are far more precise, higher—and more effective—doses of radiation can be used with less chance of damaging surrounding tissue.
Regardless of the form of external radiation therapy, treatment courses usually run five days a week for about seven or eight weeks, and are typically done on an outpatient basis.
Proton Therapy
While X-rays are currently the main method of treating tumors with radiation therapy, facilities that perform proton therapy are slowly becoming more commonplace. Worldwide, says Alfred R. Smith of the M. D. Anderson Cancer Center in Houston, there are more than six medical institutions with proton machines in the United States, and five more are in the planning or construction stages.
The advantage of using protons over other external beam sources is the precision with which protons of energetic particles are aimed at a targeted prostate cancer tumor while not affecting surrounding tissue. This direct attack on cancerous cells ultimately causes their death as the cell is particularly vulnerable to attack due to their rapid cell division. Proton treatment is notably valuable for treating localized, isolated, solid tumors before they spread to other tissues and to the rest of the body.
However, issues of cost and access have hampered wider use. Today’s proton-therapy machines take up a considerable amount of room owing to the large magnets that create the energetic particles and the concrete walls that are needed to shield the radiation. These machines also come with a hefty cost—between $25 and $150 million—allowing only a handful of cancer centers the ability to purchasing such equipment.
As efforts are made to reduce the size of these machines, the cost to build them and the price tag for treatment should also fall—giving cancer patients more accessibility to this treatment option. A machine now being developed by researchers at Lawrence Livermore National Laboratory is expected to be a fifth of the size and cost of the proton-therapy machines that are currently found at six specialized medical centers in the United States. Five more centers are currently under construction in the U.S.
Brachytherapy
With brachytherapy, tiny little metal pellets containing radioactive iodine or palladium are inserted into the prostate via needles that enter through the skin behind the testicles. As with 3D conformal radiation therapy, careful and precise maps are used to ensure that the seeds are placed in the proper locations.
Over the course of several months, the seeds give off radiation to the immediate surrounding area, killing the prostate cancer cells. By the end of the year, the radioactive material degrades, and the seeds that remains are harmless.
Compared with external radiation therapy, brachytherapy is less commonly used, but it is rapidly gaining ground, primarily because it doesn’t require daily visits to the treatment center.
The Importance of Dose Planning
Just as surgical skill can play an important role in determining outcomes from prostatectomy, technical skill and manual dexterity can play an important role in determining outcomes from radiation therapy. The use of computer software to assist with the dose planning and target prostate tissue helps greatly, but, in the end, the skill and experience of the radiation oncologist will make the biggest difference.
When choosing a radiation oncologist, at a minimum, make sure he or she has broad experience with an assortment of approaches and can objectively help to decide on the best course of treatment.
Additional Reading:
Chapter 2: Initial Treatment: Weighing the Pros and Cons of Each Option: Radiation Therapy
Questions to Ask Your Doctor When You're Considering Radiation Therapy for Early-Stage Disease
Prostate Cancer News: Treatment and Outcomes
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