Radiation therapy is a method often used in the treatment of prostate cancer. What it does is damage the DNA of cancer cells by exposing them directly to radiation. When a cancer cell’s DNA is damaged, it prevents the cell from growing and ultimately destroys it.

Radiation therapy is usually administered during the localized stage of prostate cancer, or when the cancer cells have not yet spread to surrounding organs or tissues. This is when radiation therapy is most effective.

To determine whether a patient’s prostate cancer is in the localized stage, the doctor considers the following:

• Tumor grading – This is determined by a prostate biopsy. This test makes it possible to tell whether or not if there are cancer cells within the prostate. If cancer cells are found, then the pathologist will give the patient a point score, known as a Gleason score, based on the aggressiveness of the cancer. A high score means that the tumor is highly aggressive, whereas a low score means that the tumor is not too aggressive.

• Duration of the cancer – This is determined by examining the size of the tumor, and by measuring the extent of which the cancer has spread to nearby lymph nodes and other organs that are not directly connected to the prostate.

• The level of Prostatic-Specific Antigen (PSA) in the blood – In addition to helping the doctor determine whether the cancer is in the localized stage, a patient’s PSA levels tell us about the cancer’s risk level. This is important, as the risk level will be a determining factor in deciding which radiation therapy option is most suitable.

Localized prostate cancer is broken down into 3 types:

• • Low-risk prostate cancer: which has a PSA level of ≤ 10 nanograms/milliliter (ng/mL), a Gleason score of ≤ 6, and are in stages T1c to T2b (from four T-Stages in total: T1-T4).

• • Intermediate-risk prostate cancer: which has a PSA level of > 10 nanograms/millileter (ng/mL), a Gleason score of ≥ 7, and are in stage ≥ T2c.

• • High-risk prostate cancer: which must have at least two of the following three characteristics: PSA level of > 10 nanogram/millileter (ng/mL), a Gleason score of ≥ 7, and are in stage ≥ T2c.

Types of Radiation Therapy Used to Treat Prostate Cancer

There are 3 main treatment options:

• External beam radiation – External beam radiation is often delivered using a technique known as image guided radiation therapy (IGRT). When using IGRT, the doctor can view images of the patient’s tumor, or the area at which radiation must be targeted, and is able to use those images to help construct a treatment plan. The doctor will implant 3 small metallic markers into the prostate to determine the position at which radiation must be beamed during treatment. This ensures that the focus of the radiation is as accurate as possible, and that nearby healthy tissue is kept safe and exposed to as little radiation as possible. In this way, IGRT helps to reduce side-effects of radiation therapy and has more control over the cancer. The IGRT technique is most commonly used with low to high-risk prostate cancer patients

• Brachytherapy (radioactive seed implantation) – uses small pellets of radioactive material that are inserted directly into or very close to the patient’s tumor. In cases of prostate cancer, there are 2 types of brachytherapy:
• • Low-dose rate (LDR) interstitial brachytherapy, also known as permanent implantation, uses tiny pellets containing iodine-125, which omit small amounts of radiation to which the tumor is then exposed. This technique allows the pellet to release its radioactive material slowly and in gradually decreasing quantities. The pellet can remain in the prostate permanently, and it does not need to be removed once its radioactive material has been depleted. Permanent brachytherapy is used to treat cases of low-risk prostate cancer.

• • High-dose rate (HDR) interstitial brachytherapy, also known as temporary implantation, is the temporary insertion of radioactive material inside or near the tumor. Temporary implantation is able to use materials which apply the highest amount of radiation to the tumor, while minimizing exposure to nearby organs and healthy tissue.

With temporary implantation, the implant is inserted through a microscopic catheter using transrectal ultrasound (TRUS). This allows the doctor to control the intensity (strength) of the radiation, and to focus higher or lower levels of radiation on different areas of the prostate. When the implant is removed, no radioactive material will be left over. Temporary implantation with high levels of radiation is often used in cases of medium to high-risk prostate cancer.

• External Beam Radiation Therapy Combined with Seed Implantation – With this method, the doctor will use thevolumetric modulated arc therapy technique, which is a type of intensity modulated radiation therapy (IMRT). This technique has been developed to increase the accuracy of radiation and minimize the exposure to nearby organs, and when combined with high dose rate (HDR) interstitial brachytherapy (HDR), its treatment results are highly effective. The doctor will decide whether or not this technique is appropriate for each individual patient.

When selecting a treatment option, the doctor will consider factors such as the position, size, and how much the cancer has spread, as well as the patient’s age and the level of pain likely to be caused by treatment. Bumrungrad International Hospital is fully prepared, in terms of staff expertise and comprehensive treatment technology, to provide patients with the widest range of options when considering which treatment option is the most suitable.

Possible Side-Effects

With radiation therapy to treat cancer, side-effects usually arise when nearby organs or tissues connected to the tumor are exposed to radiation. The side-effects that a patient may experience will depend on the area of the tumor. In cases of prostate cancer, the bowel or the bladder will experience most of the side-effects. Inflammation of the rectum, diarrhea, or blood in stools, for example, occurs in around 1-4% of cases, while inflammation of the bladder and blood in urine occurs in less than 1% of cases.

Currently, however, the use of radiation therapy in the treatment of prostate cancer is highly efficient. It reduces many of the complications that prostate cancer patients worry about most, such as erectile dysfunction and incontinence.

It can be said that prostate cancer treatment using radiation therapy, in addition to producing excellent treatment results, can also prevent new health problems from emerging.
 

B y Dr. Apichart Panichevaluk , Radiologist, Horizon Cancer Center, Bumrungrad Hospital

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