Radiation Therapy

Radiation involves the killing of cancer cells and surrounding tissues with directed radioactive exposure. 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

This is the most common type of radiation therapy. CT scans and MRIs are used to map out the location of the tumor cells, and X-rays are targeted to those areas. With 3-D conformal radiotherapy, a computerized program maps out the exact location of the prostate tumors so the highest dose of radiation can reach the cancer cells within the gland.

Intensity-modulated radiation therapy (IMRT) allows the radiation doctors to modulate, or change, the intensity of the doses and radiation beams to better target the radiation delivered to the prostate, while simultaneously delivering lower doses to the tumor cells that are immediately adjacent to the bladder and rectal tissue. These techniques are always improving, including the use of guidance markers (fiducial markers), which may be able to reduce the risks to the bowel and bladder over time.

Because the treatment planning with these types of radiation therapy is far more precise, higher—and more effective—doses of radiation can be used with less chance of damaging surrounding tissue. Also, because radiation works slowly, toxicities to the normal surrounding tissues can also develop slowly.

Many studies have shown that while surgery results in a more immediate loss of erectile function followed by a period of recovery, radiation therapy results in a slower loss of erectile function over time in men who have good erectile function before treatment. By the end of five years, the risks of erectile dysfunction appear to be fairly similar in men who have chosen radiation or surgery.

Regardless of the form of external radiation therapy, treatment courses usually run five days a week for about seven or eight weeks, and are done on an outpatient basis.

Proton Therapy

The advantage of using protons over other external beam sources is precision. Protons of energetic particles can hit a targeted prostate cancer tumor without affecting surrounding tissue. This direct attack on cancerous cells ultimately causes their death, as the cells are particularly vulnerable to attack due to their rapid division.

Proton treatment is notably valuable for treating localized, isolated, solid tumors before they spread to other tissues and the rest of the body. However, to date, proton beam therapy has never been compared directly to standard IMRT techniques, so we do not truly know if this offers an advantage over standard approaches.

Issues of cost and access have also hampered wider use. Today’s proton-therapy machines take up lots of room, owing to the large magnets that create the energetic particles and the concrete walls needed to shield the radiation.

The machines also come with a hefty cost—between $25 and $150 million—so only a handful of cancer centers can purchase such equipment. There are currently very few medical institutions with proton machines in the United States.

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 machines in use today.


With brachytherapy, tiny metal pellets containing radioactive iodine or palladium are inserted into the prostate via needles that enter through the skin behind the testicles. As with 3-D 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 remain are harmless.

Compared with external radiation therapy, brachytherapy is less commonly used, but some patients prefer this option primarily because it doesn’t require daily visits to the treatment center. Side effects can include erectile dysfunction, urinary frequency and obstruction, and rarely rectal injury.

The Importance of Dose Planning

Just as surgical skill can play an important role in determining outcomes from prostatectomy, the technical skill and manual dexterity of your radiation oncologist can play an important role in radiation therapy outcomes.

The use of computer software and 3-D technology to assist with dose planning and targeting of prostate tissue helps greatly, but 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 you decide on the best course of treatment.

Terms to know from this article:


A procedure in which radioactive material sealed in needles, seeds, wires, or catheters is placed directly into or near a tumor. Also called internal radiation, implant radiation, or interstitial radiation therapy.


An operation to remove part or all of the prostate. Radical (or total) prostatectomy is the removal of the entire prostate and some of the tissue around it.


A doctor who specializes in treating cancer. Some oncologists specialize in a particular type of cancer treatment. For example, a radiation oncologist specializes in treating cancer with radiation.


A mass of excess tissue that results from abnormal cell division. Tumors perform no useful body function. They may be benign (not cancerous) or malignant (cancerous).


An organ that makes one or more substances, such as hormones, digestive juices, sweat, tears, saliva, or milk. Endocrine glands release the substances directly into the bloodstream. Exocrine glands release the substances into a duct or opening to the inside or outside of the body.

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