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Gynecologic Cancers
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| The content below was developed by Mitchell Kamrava, MD. Please email any questions/comments about this site or Gynecologic Cancers in general to mkamrava@mednet.ucla.edu |
Gynecologic Cancers: What You Should Know
Types of Radiation Treatment
- External Beam Radiation
3D Conformal
IMRT/IGRT
SBRT - Brachytherapy
Image Guided Brachytherapy
Types of Image Guided Brachytherapy
Intracavitary
Interstitial
Here at UCLA we have a strong and diverse dedicated team of physicians dedicated to the care and management of women with gynecologic malignancies. We meet weekly to discuss cases as a group in order to provide an integrated an comprehensive treatment plan for patients. Our multidisciplinary gynecologic cancer team includes:
Radiation Oncology: Mitchell Kamrava, Jeffrey Demanes
Gynecologic Oncology: Robin Farias-Eisner, Oliver Dorigo, Sanaz Memarzadeh, Amer Karam, James Heaps
Medical Oncology: Gottfried Konecny, John Glaspy
We provide radiation services both at the UCLA Westwood campus and Santa Monica campus. Below is a description of the types of treatments that are commonly used in the management of gynecologic malignancies.
External beam radiation therapy (EBRT)
3D conformal therapy
This is a radiation technique where multiple radiation beams are used to conform to a target. The dose of radiation that is delivered from each radiation field is shaped by small leaves in the head of the radiation treatment machine called multileaf collimators. The intensity of the radiation from each field is uniform which is different than with intensity modulated radiation therapy (IMRT). Below is an example of what the treatment fields look like on an X-ray when treating the pelvis.
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*Images from wikibooks -- In the image on the left, the red outline depicts the borders of the radiation field on this “AP” (anterior-posterior) X-ray film. The striped lines in the corners represent areas where the radiation is blocked from penetrating. The colored structures in the middle of the field represent contours of normal organs and the areas being targeted for radiation. The image on the right represents a representative pelvic field on a lateral X-ray. Below is an example of the distribution of the radiation dose on an axial CT scan using this type of “4-field box” approach. |
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One can see that the radiation dose covers the entire pelvic region but the actual target on this slice, which can be seen in the pale blue outlines on the right and left sides of the pelvis, is actually much smaller. Ideally we would be able to sculpt the radiation to these pale blue regions and to spare the middle part of the pelvis from unnecessary radiation. Advances in radiation with intensity modulated radiation therapy (IMRT) give us the ability to accomplish this. |
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Intensity modulated radiation therapy with image guidance (IMRT/IGRT)
IMRT is a treatment advance that allows us to modulate the intensity of the radiation dose within a given radiation field. This means that the distribution of the radiation dose can be sculpted more finely around targets of interest while sparing more normal tissues. An example of this can be seen below where the axial CT image on the left is an example of a 3D-conformal plan and on the right is an example of an IMRT plan on the same patient. One can see that the IMRT plan allows the majority of the dose to be placed around the lymph nodes (which is the target) while sparing the bowel centrally.
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In this other sagittal view one can also appreciate that less dose to the bladder (yellow) and rectum (brown) can be achieved with the IMRT plan on the right compared with the 3D-conformal plan on the left. |
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Here at UCLA we have multiple state of the art radiation treatment machines that are capable of IMRT. These include: Tomotherapy, TrueBeam, NovalisTX, and ViewRay (coming soon)
Because the radiation dose is more sculpted with IMRT it is critical that the patient be set up properly each day. Image guidance (IGRT) is used to verify your position and anatomy prior to your treatment to ensure that the intended radiation targets are being treated properly. Any adjustments in your setup are made and then when 100% certainty is achieved the treatment is delivered.
Stereotactic body radiation therapy (SBRT)
This is a specialized type of external beam radiation that allows highly precise delivery of high doses of radiation to small targets. Typically treatment with this technique is completed in 3-5 treatments over the course of 1-2 weeks. This is opposed to the daily standard external beam radiation treatment that is typically given over the course of multiple weeks.
This technique is currently being used in situations where treatment options have previously been limited. One example of a situation where SBRT has been used was in a patient with endometrial cancer who developed an isolated recurrence at the edge of her previous radiation field in the para-aortic region. We created an SBRT plan where the patient was treated in 5 treatments over the course of about 1 week. She was treated as an out-patient and was able to continue with her regular daily activities without any difficulties. Because of this treatment option she was able to avoid having to have surgery. Below are some images of her radiation treatment field:
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The first image shows the recurrent lymph node outlined in red. The second row shows images (axial, coronal, and sagittal) of the distribution of the radiation dose that was delivered to this area. |
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Brachytherapy (brake-ee-therapy) is the oldest type of radiation treatment and was used well before the development of modern day linear accelerators that are used for external beam radiation therapy. It is used in the management of almost all cancers but most commonly in the treatment of gynecologic, breast, and prostate cancers.
The greatest advantage of brachytherapy is that the treatment is from “inside out” as opposed to “outside in”. This means that instead of radiation traveling through normal tissues that don’t need to be exposed in order to reach a target located in the body brachytherapy allows a small radiation source to be brought directly to and/or near the target. This allows the greatest amount of radiation dose to be concentrated where it is needed most and the intensity of the radiation falls off very quickly thereby minimizing unnecessary radiation dose to your normal tissues.
Here at UCLA we have extensive experience in brachytherapy and in particular High Dose Rate (HDR) brachytherapy. With HDR brachytherapy a single tiny (4.5 mm diameter) radioactive source of Iridium-192 is laser welded to the end of a thin, flexible stainless steel cable and is housed in a device called an afterloader. This computer guided afterloader directs the source into the treatment catheters or applicator that has been placed in the patient by the brachytherapy physicians. The source travels through each catheter in 5 mm steps, called “dwell” positions. The distribution of the radiation dose is determined by the dwell positions the source stops at and the length of time it dwells there. This ability to vary the dwell times is like having an unlimited choice of source strengths. This level of control is possible only with HDR. After the HDR treatment the source retracts into the afterloader. The patient is no longer radioactive. Finally, because the afterloader controls the radiation source, radiation exposure to the physicians, hospital staff and family members is eliminated.
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On the left is an example of what a remote afterloader looks like. The middle picture shows what the inside of the afterloader looks like with the cover off. The image on the right shows how a small radiation source is welded onto the end of a cable. The motor in the afterloader pushes and pulls this cable in and out of the treatment channels. |
Recently we’ve acquired the most technologically advanced HDR remote afterloader called the Flexitron. We are currently one of only a few centers in the United States to have this afterloader.
Image guided brachytherapy is a significant advance in the treatment of gynecologic malignancies but is highly technique dependent and is done best by centers that have a high volume of cases. Prior to image guided brachytherapy 2D images were taken with brachytherapy applicators and doses were prescribed to points.
In the images below for example on the right is an anterior-posterior view of a vaginal applicator inserted in the vagina. You can see the cylinder pushing up against the top of the vaginal apex. You can’t see the outline of the entire bladder and rectum but one way to approximate them is to place foley catheters in the bladder (yellow outline) and the rectum (brown outline) so they can be visualized.
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An alternative to this is to use CT compatible applicators and to use CT imaging. The advantage of this is that CT imaging allows you to see the anatomy in more detail than on X-rays. For example, a CT image with a vaginal applicator in place looks like the following:
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One can actually “see” the anatomy including the bladder (yellow) and rectum (brown). The cylinder is outlined in red. By being able to clearly see things we can more effectively optimize the radiation dose to the target and limit the dose to normal tissues. |
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Types of image guided brachytherapy
Intracavitary
While most institutions only offer a single channel intracavitary applicator to treat the vaginal apex we offer multiple multichannel applicators as well as a single channel applicator. The multichannel applicators that we offer include:
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CET Multichannel vaginal cylinder |
CET Demanes-Rodriguez cylinder and ovoids applicator |
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| CAPRI applicator (Varian medical) | The single channel applicator that we offer is: Xoft electronic brachytherapy |
Our preference for using a multichannel applicator is based on research from our group published in 1999 that shows that a multichannel cylinder with 7 channels can reduce bladder and rectal doses by 15% or more than commonly used single channel applicators (Int. Journal Radiation Oncology, Biology, Physics, 1999). This work was based on 2-dimmensional planning and so we’ve redone this work with 3D-planning using a 13 channel applicator and once again show that multichannel applicators significantly reduce dose to the bladder and the rectum compared to single channel applicators. This data was presented at the World Congress of Brachytherapy in Barcelona in 2012 and was selected as one of the top 20 posters of the entire conference.
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Below is a series of cartoons to help better illustrate the advantages of a multichannel applicator over a single channel one. The first image shows a radiation source (blue rectangle) and demonstrates that radiation is distributed equally in all directions from the radiation source. The most intense dose of radiation is nearest the radiation source (dark red circle) and the radiation dose gets less and less the farther away from the source you go.
In the picture on the left you can see the bladder in yellow, the vagina in the blue cylinder, the brachytherapy applicator in the light blue rectangle with the radiation dwell positions in red, and the rectum in brown. With a single channel applicator the radiation dose spreads out from the central part of the applicator essentially in circles and because there is only one channel you can not alter the shape of this radiation distribution. So if there is an area of radiation dose that overlaps the bladder or rectum there is little that you can do about this.
In the picture on the left you can see an example of a 3 channel applicator. Based on computer programming we can figure out a patient specific pattern for the radiation dwell positions so we can keep more radiation dose off of the bladder and the rectum. We can accomplish this because having multiple channels gives us more dwell positions and therefore more flexibility in sculpting the radiation dose.
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Below is an actual example of the CAPRI applicator (a 13 channel applicator) and the distribution of radiation dose that was delivered around the vaginal apex (right image axial and left image sagittal). Below this is a 3D depiction of the anatomy and distribution of the radiation dose (bladder in yellow, rectum in brown, applicator in purple, radiation dose in red):
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3D depiction of the anatomy and distribution of radiation dose. |
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Intracavitary applicators are also used to treat cervical cancer and the most commonly used applicator is a tandem and ovoid applicator.
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Our approach at UCLA is to do 3D based instead of 2D based planning for these cases as well. An example of 2D based planning using a tandem and ovoid applicator can be seen below.
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Example of 2D based planning: |
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An example of 3D based planning can be seen below with an axial image on the left and a coronal image on the right.
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Once again one can immediately appreciate how much additional detail in the anatomy and distribution of the radiation dose can be appreciated on the CT scan versus the X-ray.
Interstitial
Interstitial refers to brachytherapy treatment where there isn’t a cavity for a radiation applicator to fit into and so a series of small hollow little tubes are placed in and near the target tissue. An example of when this might be used is shown in the following illustrations. In the picture on the left there is an oval uterus narrowing down to the rectangular cervix which has a red cervical cancer and a larger rectangular vagina. Ideally after an initial course of external beam radiation therapy and concurrent chemotherapy this red cervical tumor will shrink and allow for a tandem and ovoid applicator (green figures) to fit into the vaginal fornices and cervix so the appropriate distribution of dose (orange) can be achieved (image on left).
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Sometimes a lesion does not regress at the end of external beam radiation and may not allow the tandem and ovoid applicator to properly fit as in the picture on the right. |
In other cases the tandem and ovoid applicator would fit but the residual lesion is larger than the standard distribution of dose with this applicator and so some of the tumor would be underdosed if this approach were used as is illustrated below on the left.
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So in these cases an interstitial approach is best so that the residual disease can be appropriately encompassed as can be seen on the right. |
Below is a 3D rendering of the distribution of radiation dose and normal tissues from a gynecologic interstitial implant:
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An axial CT slice showing the distribution of small hollow brachytherapy tubes and the distribution of radiation dose for a gynecologic interstitial brachytherapy implant. |
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