Carolyn Vachani, RN, MSN, AOCN
Abramson Cancer Center of the University of Pennsylvania
Last Modified: December 10, 2006
HDR is a type of internal radiation given for some uterine or cervical cancers. HDR stands for high dose rate, which means the woman receives a high dose of radiation over a brief period of time, as compared with LDR (low dose rate), in which the radiation is delivered internally over several days or external beam radiation, which is given over a period of weeks. HDR allows for more precise delivery of high doses of radiation to the tumor, while minimizing the amount of radiation normal tissues receive (such as the bladder and rectum).
HDR is given by inserting a probe, also called an applicator, into your vagina. This probe is connected to a machine that houses a radiation source. The machine automatically feeds the radiation source into the probe, where it remains for a predetermined time, known as the dwell time. Once the time is up, the machine removes the source and the applicator is removed from your vagina. The dwell time can be anywhere from 10-20 minutes and during this time you will be alone in a lead lined room. This room is to protect the technicians from receiving radiation, but they can see you through a glass window and speak to you via a two way microphone.
Your doctor may recommend HDR in conjunction with traditional external beam radiation (EBT), in which case it is typically given one day a week along with 4 days a week of EBT. Some women will receive HDR after they have completed EBT. You will receive HDR from 3 to 6 times, depending on the type and extent of the tumor being treated. This article will explain the procedure in detail and what you can expect. Be sure to talk to your doctor or nurse about any questions you may have. This procedure can be scary, but knowing what to expect can help to make it a little easier.
The simulation, also called set-up, allows the radiation oncologist and physicist to plan your treatment doses using CT scans of the area to be treated. For the simulation, you will come to the radiation clinic and meet with your nurse, who will ask you some questions about your health and history. If you are also receiving external beam radiotherapy in addition to the HDR brachytherapy, you will have an IV inserted and be asked to drink an oral contrast. You will then be taken to a CT scanner, where several scans will be taken. These scans are then used to plan the radiation treatment, which can take several days. Scans will be taken with and without (if you are receiving external beam radiotherapy) the applicator in place. You will return at a later date for the actual treatment.
On the day of HDR treatment, you will come to the radiation clinic, where you will meet with your nurse and doctor. You will be taken into an exam room where you will have a pelvic exam and be asked to report any problems you may be having. You will receive a medication to help you relax during the procedure. Some patients will have a foley catheter placed into the bladder. A contrast dye is put into the catheter, which allows the technicians and physicians to see the location of the bladder when giving the HDR treatment. During the pelvic exam, two gold “seeds” will be placed at the top of the vagina to allow the team to know the exact location of the vagina during the treatment (the seeds can be seen on an x-ray, whereas the vaginal tissue cannot). These seeds will fall out after about two weeks and you may or may not notice them. They are not radioactive and you can safely throw them in the trash.
You will then be taken to the HDR treatment room. You will be asked to lie on a table with your legs in stirrups. The doctor will insert the applicator into your vagina. The applicator is about one inch in diameter and gauze will be inserted around the applicator to prevent it from moving during the treatment. In some cases, a woman will need to have a small tube inserted in the rectum, through which a small amount of barium will be administered. This will allow the team to see the rectum on the x-rays used to plan the treatment. This can be scary as it is a lead lined room and you will be positioned on the table and left alone in the room. The team can see and communicate with you through a glass window and two way microphone.
A typical applicator
The HDR treatment room
Once you are positioned, your team will leave the room to take x-rays, confirm that the applicator is in the correct position, and make any necessary adjustments. This can take 15-20 minutes. Remember that they can see and hear you, so you can let them know if you are having any problems.
Once the positioning is checked by x-rays, the applicator is connected with thin wires to the HDR machine, which houses the radiation source. A physicist has calculated the appropriate dose for you ahead of time based on the simulation done earlier. This calculation determines how much radiation will be used and how long it will need to remain in place. Once everyone has left the room, the HDR machine dispenses the radiation source into the applicator. You will not feel this, but you may hear the noise of the machine. The amount of time the source will remain in the applicator can be anywhere from 10-20 minutes, depending on the type and extent of the tumor. The doctor can tell you ahead of time how long the radiation will remain in the applicator so you are prepared. Once the time is up, the machine removes the radiation source and returns it to the housing, making it safe for the team to enter the room again. The applicator and foley catheter will be removed at this time and you will be able to go home.