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Monday, May 30

Radiation for prostate cancer

Here's everything you need to know about this treatment option.

Men who have been diagnosed with prostate cancer have several options for their next step. Many men with slow-growing, low-risk cancer choose active surveillance, a wait-and-see approach that tracks cancer's progress.

Other treatments are recommended if the cancer is at a higher risk (a Gleason score of 7 or higher) or has already spread. (On a scale of 6 to 10, a Gleason score classifies prostate tumour cells.) The greater the number, the more likely it is that cancer will spread. There are two options: surgery to remove the prostate (known as a prostatectomy) or radiation to kill cancer cells.

Studies comparing these two approaches show that neither has an advantage in terms of cancer control. Your path will be determined by factors such as your current state of health, the specifics of your cancer, and your personal preferences. However, for many men, radiation therapy may be the better option.

"It's much more precise than traditional radiation used for other types of cancer," says Dr. Anthony D'Amico, a radiation oncologist at the Harvard-affiliated Dana-Farber Cancer Institute and Brigham and Women's Hospital.


 

The two main ways to give radiation to the prostate are through external beam radiation and brachytherapy.


Are you a potential candidate? Radiation may be recommended by your doctor depending on a number of factors, including your age, health, and personal preferences. Most of the time, the type of radiation used is based on your risk level (low, medium, or high) and whether or not cancer has spread.

Hormone therapy (also known as androgen suppression therapy, or ADT) is sometimes administered prior to or concurrently with radiation. ADT lowers levels of male hormones known as androgens, which can slow or even stop the growth of cancer. Studies have shown that this combination is better than radiation alone for men with localized prostate cancer and a Gleason score of 7 or higher.

If you choose surgery, your doctor may recommend adjuvant radiation therapy afterward. "You have surgery to remove the cancer, and then radiation to eliminate any remaining tumor deposits to keep the cancer from returning," explains Dr. Anthony D'Amico of Harvard's Dana-Farber Cancer Institute. Cancer that has spread beyond the prostate gland may also necessitate post-surgery radiation.

Following radiation, you will have a prostate-specific antigen (PSA) test every three to six months for the next five years, and then annually after that to check for cancer recurrence. If your PSA ever rises above 2, imaging tests are performed, and if additional radiation or other appropriate treatment is required, "explains Dr D'Amico."


External beam radiation 

high-energy radiation rays are directed at the prostate cancer site (and sometimes nearby lymph nodes). External beam radiation destroys cancer cells effectively, but it can also harm healthy tissue. A CT scan pinpoints the exact location of the prostate gland, allowing for more precise focusing and limiting collateral damage to the rectum and bladder. For five to ten minutes, you lie on a table while a device emits radiation. Treatments are typically given five days a week for several weeks. External beam radiation therapy is classified into several types:


Conformal radiation therapy in three dimensions (3D-CRT)
Before treatment, three-dimensional images of the prostate and surrounding structures are taken to pinpoint their locations. The radiologist can use these images to keep radiation away from the bladder and rectum.

Radiation therapy with intensity modulation (IMRT).
 IMRT is now the most popular type of radiation therapy. It is similar to 3D-CRT in that it allows doctors to change the radiation intensity within each of several radiation beams, increasing total radiation to the cancerous area while decreasing radiation to healthy tissues.

Treatment with proton beams 
This has the same precision as IMRT, but instead of photons (light particles), it uses protons (subatomic particles with a positive electrical charge). Radiation is released in a narrow band during proton beam therapy, minimizing damage to surrounding tissue. The disadvantage is that it is more expensive and not widely available. "In addition, outcomes appear to be comparable with IMRT in terms of curing cancer and improving quality of life," Dr. D'Amico says.


Treatment with stereotactic body radiation (SBRT). 

SBRT delivers multiple radiation beams to the tumour using image guidance and computer-controlled robotics. There are several systems available, with brand names such as CyberKnife, Gamma Knife, and TomoTherapy. Long-term consequences are still being investigated.


Radiation therapy with hypofractionation

Here's everything you need to know about this treatment option. This provides higher doses with each treatment, requiring fewer sessions—typically five treatments spaced out over four to five and a half weeks. Only men who have good urinary flow, do not need to urinate frequently at night, have not had prostate surgery, and do not take anticoagulants are eligible for this treatment (blood thinners).


Brachytherapy.

Brachytherapy entails inserting radioactive pellets, or "seeds," about the size of a grain of rice into or near the prostate tumour. Depending on the size of the prostate gland, the number of seeds ranges from 50 to 150.

Following either general or spinal anaesthesia, the doctor inserts an ultrasound probe into the rectum and a catheter into the bladder. The doctor then guides the seeds into place by inserting a needle through the perineum (the area between the scrotum and the anus). The seeds are left alone and gradually emit less and less radiation until they are no longer radioactive. This could take anywhere from three months to a year, depending on the type of seeds used.

If cancer returns, your doctor may recommend high-dose-rate brachytherapy. The more powerful seeds are planted here for a short time and then taken out a few days later. This process is done several times.


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