Radiation Therapy

Once you have decided to go ahead with radiation therapy, you will not be starting the radiation immediately that day.  There are several steps to go through first, namely:

  • Scans or other testing may still need to be done
  • Hormone therapy may need to be started and given for a few months before radiation can start
  • Gold marker seeds are placed in the prostate gland
  • Mapping / CT simulation is done.  An MRI scan may also be done at this time.
  • Computer planning is performed
  • A dry run of the treatment is performed, called a “V-Sim”
  • It typically takes about 3 weeks from the consultation until the first treatment.  Longer if hormone therapy needs to be started first.

Radiation dosage and treatment length

We usually use a standard radiation dosage that have been found to be safe and effective for prostate cancer.   That dose is typically the highest possible dose that is safe to give.  At my clinic the dose is 45 treatments for a total of 8100 cGy.  There is some individualization that occurs — for example if you have had your prostate removed we will use 39 treatments.

These 45 treatments are given 5 days a week on Monday – Friday for 9 weeks.  A treatment takes about 20 minutes each day, but the radiation beam is only on for a few minutes of that time.  You are given a certain time to come every day for your appointment, which is called a treatment slot.

Hormone therapy

If you have an aggressive prostate cancer you may first need to start on hormone therapy injections and be on that medication for 2 months before radiation starts.   It is not dangerous to wait those two months — the hormone therapy will cause the PSA to drop down and get the cancer “primed” for the radiation.

Gold Marker Seeds

Next, three gold marker seeds are injected into the prostate gland. This procedure is like the prostate biopsy you had.  These three tiny pieces of pure gold will remain in the prostate gland permanently.  The radiation treatment machine is able to detect the seeds, and they help the machine “lock onto” the prostate gland for more accurate targeting of the prostate gland.

Mapping / Simulation

One week after marker seed placement you will have the mapping, also known as the simulation.  During the simulation we will make an “immobilization device” which is basically a cushion that molds to your legs, that you will lie in during treatment.  This helps keep you from moving.  We will take a CT scan through your pelvis, with your legs placed in the immobilization device.  You should drink about 20 ounces of fluid about 30 minutes prior to this so that your bladder is comfortably full.  Drink the same amount of water every day before your radiation treatments.  The radiation therapist will also place a couple small tattoo marks on your skin in your hip area.  After the CT is finished, you may also be sent for an MRI scan.

Computer Planning

Next, we do the computer planning.  This takes about a week.  The radiation oncologist looks at the CT scan on the computer screen and circles the prostate gland, and prescribes the radiation dose.  The dosimetrist takes over and runs a computer program that figures out how strong the radiation beams will be, and from what angles they will enter the body.  Basically, a computer plan is created that is totally individualized for you and it will control the radiation machine during your treatment.  The radiation oncologist examines and approves the computer treatment plan.  Next the physicist will run your computer plan with a “dummy phantom” on the treatment machine.  The dummy has radiation sensors inside, and the physicist can ensure that proper dose is being given to the proper area.

The V Sim

Finally it is almost time for the treatment.  You may have a “V-Sim” first, which is not an actual treatment it is more like a “dry run”.  You will come into the treatment room for the first time, and you will get set up onto the treatment table.  The treatment machine will take a CT scan through your pelvis, and they will use the gold marker seeds to get you all lined up.  The radiation oncologist will review that everything lines up properly. You may or may not receive your first treatment immediately following the V-Sim.

Treatment Slots

You will be given a treatment time to come every day for treatment.  Treatments are Monday – Friday.  If you cannot come at your designated time one day, just let the therapists know in advance and they’ll usually be able to find a different time for you to come.

A Typical Treatment

Each day you will come in at your appointment time. The therapists will bring you into the radiation treatment room.  You will lie down on the treatment table, with your pants and underwear pulled down to you knees and a towel covering you.  Your legs will be in the “immobilization device” so that you cannot wiggle around much.  The therapists will then move the treatment table (up – down / left – right / in – out / tilt / roll) so that the tattoo marks on your skin line up with laser lights in the room.  The therapists will then leave the room and the machine will do a CT scan through your prostate area. Your bladder, rectum, prostate, and the gold markers show up on this scan.  The computer screen shows the therapist where the marker seeds are, and exactly where they are supposed to be.  The table is then finely adjusted to make the seeds are lined up perfectly.  Next, the treatment is run.  The treatment machine will rotate slowly around the treatment table, and it will pause at different angles for the radiation beam to be delivered.  Some machines will stop at 7 different angles, other machines will continuously rotate around you.  The radiation beam will be on for a few minutes in total.  When the beam is on, you may here clicking noises from the aperture shaping the beam and adjusting its intensity.  You cannot feel or see the radiation beam, but you may smell something like ozone, and some patients may report sensations such as warmth.  Once the radiation has fished, the therapists will come in the room, lower the treatment table, and you are on your way!  The rest of the day you can do all of your normal activities with no restrictions.

For More Information

If you are getting this information as a handout, if you access this information online at prostate-center.com you can click on most of these sections to get more in-depth information.

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