Radiation Therapy for Prostate Cancer

Written by: Dr. Haake

Prostate cancer is expected to affect 238,590 men in the United States and 2013, with an estimated number of deaths at 29,720. The prostate is part of a man’s reproductive system, located in front of the rectum and under the bladder. It surrounds a tube called the the urethra, through which urine flows from the bladder. The prostate is responsible for making part of the seminal fluid that helps carry sperm during intercourse. Prostate cancer in its early stages rarely causes symptoms, though patients can have alterations in their ability to urinate from enlargement of the prostate, or have blood in the urine, or have changes in their erection capability. Cancer is often picked up by a PSA test, which subsequently leads to a biopsy. Fortunately, a large percentage of prostate cancer is found in the early stages, when it is very curable with local treatments such as surgery or radiation therapy. Patients are generally seen by a surgeon and by a radiation oncologist to help determine the best treatment for them.

Southeast Radiation Oncology staffs many centers where quality radiotherapy can be delivered, with facilities in North and in South Carolina. External beam radiation therapy for prostate cancer treatment with a machine called a linear accelerator consists of an 8 to 8 ½ week course of therapy, with treatments delivered Monday through Friday. A special type of radiation planning and targeting, called intensity modulated radiotherapy (IMRT), is utilized at all of our facilities, to minimize radiation dose to surrounding organs much better than we could even 10 years ago. Because of the ability to tailor the dose closely to the prostate, patients often receive the therapy with little or no ill effects, though some patients will get irritation to urinate, some fatigue or loose stool by the end of their treatment course. Fortunately, these symptoms are usually readily treated with medications, and are self-limited, reversing over 2-4 weeks.

In 2013, the national organization for radiation oncologists, the American Society of Therapeutic Radiation Oncology (ASTRO), publicized a notice that in select prostate cancer patients, utilization of a very short course of radiotherapy for curative treatment of prostate cancer had enough clinical followup as to be deemed a reasonable option to offer patients. This short course of treatment is also called stereotactic body radiosurgery (SBRT). It consists of a total of 5 treatments given over 2 to 3 weeks. The dose given at each treatment is higher than the standard dose given in an 8 week course of therapy, but the extraordinary accuracy allows for even less of a margin of normal tissue inclusion within the beams, allowing this therapy to be done safely. Southeast Radiation Oncology has had several years of experience using this technology at one of our facilities with a special linear accelerator called the CyberKnife, and we are pleased to offer this as yet another cutting edge method of treatment for prostate cancer patients.

Some patients are best served with a radioactive implant of the prostate using small radioisotope pellets that are implanted into the prostate, with or without supplemental external beam treatment. These implants are done under anesthesia, and several of our facilities offer this. These are done in partnership with our urologic physician colleagues. The results from treatment with a single radiation implant for appropriate patients with prostate cancer have been excellent, in excess of 90% cures reported. This type of therapy has over 15 years of followup information in the medical literature, assuring us that these treatment outcomes are permanent.

Radiation also has value in treating patients with advanced prostate cancer that has spread to other sites in the body. The initial treatment for patients with spread of prostate cancer is anti-testosterone hormone administration, a shot given every one to six months, administered by the urologist. If prostate cancer spreads or is advanced at diagnosis, the cancer has a tendency to travel to bone. Focal radiation beam therapy for a short course, one to ten treatments to an area of pain, is often effective at reducing or eliminating pain. Patients can also benefit from a new treatment with injectable intravenous Radium-223, that has been used to treat the bone sites of cancer spread by traveling by the bloodstream to the areas of disease in bone. This very targeted therapy has a minimal effect on blood counts. One of the radiation therapy facilities staffed by Southeast Radiation Oncology has been on the forefront of use and research of this agent, and has been recognized as a national leader with the experience gained with Radium-223.

Prostate cancer is the most common malignancy in American men.

  • In 2003, more than 220,000 men were diagnosed as having prostate cancer, making it the number one type of cancer in men.
  • Nearly 29,000 men died from prostate cancer in 2003.
  • More than 75 percent of prostate cancer is diagnosed in men over age 65.

Risk Factors For Prostate Cancer

Incidence of prostate cancer increases with age.

  • Median age at diagnosis in Caucasian males is 71.
  • African-American men have the highest incidence of prostate cancer in the world.
  • Heredity accounts for 5 to 10 percent of cases.

Screening For Prostate Cancer

According to the American Cancer Society, men aged 50 or older should be offered a digital rectal exam (DRE) and a PSA blood test. However, it is a good idea to visit your doctor earlier to establish a baseline PSA level so you can monitor changes.

  • Prostate specific antigen (PSA) is a valuable marker for prostate cancer although BPH or infection may also cause a rise in PSA.
  • Normal range is 0-4, however, a PSA above 3 in men younger than 60 may be considered abnormal.
  • African-American men and men with a family history of prostate cancer should be examined beginning at an earlier age.

Diagnosing Prostate Cancer

Prostate cancer is most often diagnosed through a blood test measuring the amount of prostate specific antigens (PSA) in the body. However, signs and symptoms of prostate cancer can include:

  • Changes in urinary flow: Frequency, urgency, hesitancy
  • Frequent nighttime urination
  • Painful urination
  • Blood in urine

Other conditions that may cause these symptoms include an enlarged prostate (benign prostatic hypertrophy or BPH) or infection.

Radiation Therapy Options for Treating Prostate Cancer

After a diagnosis of prostate cancer has been established with a biopsy, the patient should discuss the treatment options with a radiation oncologist and a urologist. Radiation therapy treatment options to cure prostate cancer include:

  • External beam radiotherapy
  • Prostate brachytherapy

External Beam Radiation Therapy

External beam radiation therapy involves a series of daily outpatient treatments to accurately deliver radiation to the prostate.

There are two principal methods for delivering external beam radiation.

  • 3-dimensional conformal radiotherapy (3D-CRT) combines multiple radiation treatment fields to deliver precise doses of radiation to the prostate. Tailoring each of the radiation beams to accurately focus on the patient’s tumor allows coverage of the prostate cancer while at the same time keeping radiation away from nearby organs such as the bladder or rectum.
  • Intensity modulated radiation therapy (IMRT) is the most recent advance in the delivery of radiation. IMRT improves on 3D-CRT by modifying the intensity of the radiation within each of the radiation beams. This technique allows more precise adjustment of radiation doses to the tissues within the target area, potentially allowing an increased radiation dose to the prostate and reduced doses to nearby normal tissues. Higher doses to the prostate translate into a greater chance for cure, while lower doses to surrounding organs mean fewer side effects.

Both types of external beam radiation therapy are acceptable treatment; IMRT offers advantages for some but not all prostate cancer patients. With either type of therapy, painless radiation treatments are delivered in a series of daily sessions, each under half-hour in duration, Monday through Friday for seven to ten weeks overall.

Potential side effects, including fatigue, increased frequency or discomfort of urination, and loose stools, typically resolve within a few weeks after completing treatments. Impotence is also a potential side effect of any treatment for prostate cancer. However, many patients who receive radiation therapy for prostate cancer are able to maintain sexual function.

Prostate Brachytherapy

Prostate brachytherapy, better known as a seed implant, is often done in the operating room.

There are two methods of delivering internal radiation for prostate cancer:

  • Permanent seed implants
  • High-dose rate temporary seed implants

These treatments are designed to deliver a very high dose of radiation to the tumor by inserting radioactive seeds directly into the prostate gland under ultrasound guidance while the patient is under anesthesia. Isotopes of iodine or palladium are most commonly used. The seeds are approximately four millimeters long and less than a millimeter in diameter. In certain situations, both prostate brachytherapy and external radiation may be recommended to combat the tumor.

The side effects from seed implants are similar to those experienced with external beam radiotherapy. Patients usually experience urinary frequency and discomfort in urination. These effects may be lessened with medication and usually dissipate over the course of three to six months.

Proton Beam Therapy

In a few parts of the country, proton beam therapy is being used to treat prostate cancer.

Proton therapy is administered much the same way as external beam therapy, but it uses protons rather than x-rays to irradiate cancer cells.

Hormone Therapy

Certain patients may benefit from hormone therapy in addition to radiation. In some patients, hormone therapy works with radiation therapy to improve cure rates.