Gold Marker Seeds
All patients who undergo CyberKnife to the prostate gland are required to have 3 – 4 gold marker seeds injected into the prostate gland prior to doing treatment. This is because the CyberKnife machine cannot see the prostate gland, but it can see gold seeds. These markers help CyberKnife “lock onto” the prostate gland during treatment, to ensure that the radiation beams are always aimed at the prostate. A CyberKnife treatment takes about 30 minutes, and the machine x-rays the marker seeds every minute during that time, and adjusts its aim if there is any prostate movement that occurs.
Gold marker seeds are very small, each one is like a small piece of wire, about 1/4 inch in length and 1/32 inch in diameter. They are also called fiducial markers or marker seeds. They are almost solid gold, and they are not radioactive. They do not react with your body. They remain in the prostate gland permanently and they cannot be removed.
When we place the seeds we do not try to place them where the cancer is. We simply place 2 on the right side of the prostate, and 2 on the left side of the prostate. Later when we do the mapping CT scan, we outline the prostate gland and the marker seeds, and the computer and CyberKnife machine then knows exactly where the prostate is located in 3-dimensions relative to the marker seeds.
Some stereotactic treatment machines such as the TrueBeam and Tomotherapy do not require marker seeds, they are optional. The treatment machine can do a quick scan before each treatment and the treatment table moved slightly so that the prostate gland becomes centered in the treatment. This is not quite as accurate as using marker seeds, but I have done this for some patients who do not want to be put through the procedure of having the marker seeds placed. In addition, these machines can not automatically check the location of the prostate during the actual treatments, so if there is any patient or prostate movement during the treatment then there may be some mis-aiming.
SpaceOAR Hydro Gel
SpaceOAR hydrogel is an exciting addition to prostate radiation therapy. Currently only a handful of centers across the country are using this technology. A gel is injected into the tissue space in between the prostate gland and the rectum. Usually those two organs are directly against each other, but by injecting a gel we can push them apart. This results in less radiation dose reaching the rectum! With less radiation dose there are clinically proven fewer rectal side effects, and a smaller chance of rectal complications. With SpaceOAR there may also be less radiation reaching the penile bulb, and less erectile dysfunction.
Approximately 10cc (1/3 ounce) of two liquids are simultaneously injected via a Y connector and a long needle into the tissue space between the prostate and the rectum. When those two liquids mix together they create a firm gel in the tissue space. The gel remains there for about 3 months and then begins to break down, eventually being completely absorbed by the body.
SpaceOAR does not usually cause side effects, but occasionally men have report a peculiar sensation or discomfort in the rectal area, which usually subsides in a few days. SpaceOAR can be used with any type of prostate radiation treatment, whether that be IMRT, proton therapy, brachytherapy, or CyberKnife/SBRT. In the picture below, the white area in between the prostate and the rectum is the hydrogel which I have injected, pushing the two nicely apart. They would normally be directly against each other.
Overview of the Gold Seed Procedure
This is a surgical procedure we do in the operating room under anesthetic. Some centers may do this step with local anesthetic only, but we find it is more comfortable to use deep sedation. In the procedure, your legs are placed in footrests and your legs are spread apart and your knees are bent up. We place an ultrasound in the rectum so that we can see the prostate gland in real time during the procedure. We use only needles — there is no cutting and no suturing required. The procedure takes about 10 minutes if we are just placing gold markers, and it takes about 20 minutes total if we are also placing SpacOAR.
The needles go through the perineum, which is the patch of skin in between the testicles and the anus. The needles do not go through the rectum.
Many radiation oncologists have a urologist place the gold seeds and SpaceOAR, but I prefer to do it myself. If a urologist places the marker seeds, he may insert the needles through the rectal wall to deposit the seeds. This is not bad and it will work fine, but I believe that you can aim better if the needles are placed through the perineum skin instead of through the rectum, and there will be less chance of infection. It can be finicky injecting the SpaceOAR into the perfect spot, so it is good to have a lot of experience with this.
The recovery after the procedure is usually very fast and you can go home the same day. You will need a driver because of the sedation. There may be a little tenderness. There may be a little blood in the urine or the semen over the next few days or weeks. There is a risk of infection so you will take antibiotics starting the evening before the procedure and continuing for three days after.