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The Radiation Oncology department at Mayo Clinic offers a number of advanced treatment capabilities.
The Mobetron produces electron beams.
Locally advanced cancers can be radiated during surgery with Intraoperative Radiation (IORT), an advanced radiation treatment available at Mayo Clinic Hospital in Phoenix since January 2002. Most patients also receive a 2-5 week sequence of external beam radiation (EBRT), often with concurrent chemotherapy, prior to surgical removal of the cancer (when feasible) and IORT.
IORT is delivered to cancers that cannot be safely removed by the surgeon, or to the tumor bed, a narrow area surrounding the tumor removal site. This is done while normal structures are surgically displaced out of the radiation field.
IORT is delivered using the Mobetron, a specially designed mobile linear accelerator producing electron beams (see figure). The IORT dose (1000-2000 cGy) is equivalent to an additional 2-5 weeks of EBRT.
Mayo Clinic is the only facility in the Southwest offering this treatment. Over 350 patients have received IORT at Mayo Clinic Hospital in Phoenix since the inception of the IORT program in January 2002. IORT has been used as a component of treatment in patients with locally advanced primary or locally recurrent gastrointestinal (colorectal,pancreatic, esophagus, stomach, biliary), gynecologic and renal cancers and sarcomas (soft tissue tumors) in our institution. It has also been used to replace a component of EBRT for patients with early breast cancer. (See news releases, IORT fact sheet and additional information on the Mayo Clinic Web site, Intraoperative Radiation Therapy at Mayo Clinic).
This is breakthrough treatment because many institutions do not offer curative treatment options for patients with locally recurrent cancers. The use of IORT as a component of aggressive treatment has resulted in 5-year survival ranging from 20 percent to 40 percent for patients treated at Mayo Clinic for tumor bed or nodal relapses from colorectal, gynecologic or kidney cancer and soft-tissue sarcomas. (see Clinical Publications section of this Web site regarding IORT publications)
Image-Guided Radiation Therapy combines the type of x-rays used for diagnostic imaging or CT scanning with the daily treatment beams. The physicians and therapists use daily, pre-treatment imaging to precisely adjust the radiation fields. This is important when the target is very close to sensitive structures or when the target can move within the body because of respiration or normal filling of the rectum and bladder. To make this adjustment possible, special x-ray equipment is mounted on the treatment machine, as shown in the picture.
This CT slice through a patient's pelvis shows the prostate (red) and rectum (green). WIth IMRT, the high dose region (orange) surrounds the prostate and spares the rectum. The low dose region (blue) shows the five beam directions also shown with white arrows.
Intensity modulated radiation therapy (IMRT) is a powerful new technology recently introduced in radiation oncology. During IMRT treatments, the radiation beam shapes change hundreds of times, using special mobile beam blocking devices. The dynamic blocks divide the beam into tiny beamlets whose intensities vary. The radiation dose can be made to bend around critical normal tissues in a manner unlike any other form of treatment. Because these motions are so complicated, special state-of-the-art computer programs are used to plan the treatments and to control the treatment machines during the delivery of the IMRT. IMRT is a very complex form of 3-D Conformal RT (see below section) in which the exact shape of the field is constantly changing during irradiation based on the computer generated plan.
This CT slice though a patient's head shows a target region (red), saliva glands (blue and purple), and spinal cord (orange). With IMRT, the high dose region (yellow) surrounds the target and spares the saliva glands and spinal cord.
IMRT has been used to treat patients at Mayo Clinic in Arizona since 2000. More than 100 patients each year receive IMRT for cancers in all body sites. The examples in the pictures show how the radiation doses can be reduced to critical organs such as the rectum (for prostate cancer) and the salivary glands (for head and neck cancer).
Read more about IMRT at Mayo Clinic.
At our institution, this technology is used to treat a variety of cancers at almost every location of the body. Using CT and MRI scans, a patient's tumor, areas of possible cancer spread, and normal organs are identified and reconstructed virtually on a computer in three dimensions. Radiation beam trajectories are chosen which treat the cancer, but spare normal organs. In addition, the beams are shaped to exactly conform to the outline of the tumor, thereby limiting the radiation exposure to nearby tissues. 3D conformal planning requires sophisticated computers and concentrated effort from the physician and dosimetrist. Using this technique, cancer can be treated with more accuracy and less side effects than traditional planning methods.
Nasal Tumor Example
This picture shows a CT of a patient's head. The tumor (red) is located within a patient's nasal cavity, in front of the brain. The colored lines represent incremental levels of radiation dose, devised by a 3D conformal treatment plan. The dose prescribed by the physician (violet line) closely conforms and encircles the tumor. The brain, eyes, and lenses receive only minimal doses of radiation (blue and green lines).
The high dose radiation line (in violet) surrounds the tumor (in red). The eyes, lenses, and brain receive a minimal dose from the treatment (blue line, 10 percent of tumor dose).
CT showing a tumor (red) in patient's nasal cavity.
CT showing a tumor (red) in patient's brain.
3D rendering of a patient's abdomen.
Brain Tumor Example
This picture shows a tumor (red) located within a patient's brain. The eyes (green) and jaw (gray) are also shown, along with a CT slice through the center of the tumor. The dose net (blue) shows the volume receiving a radiation dose of 6000 cGy, which conforms to the prescribed margin 2 centimeters around the tumor.
Abdominal Tumor Example
This 3D rendering of a patient's abdomen shows a high dose region (blue mesh) surrounding a target (red and purple) while avoiding other organs.
Brachytherapy is the use of radioactive seeds, wires or needles to deliver localized radiation in or near a tumor in an effort to destroy the cancer. The advantage of brachytherapy is that a concentrated dose of radiation is placed directly in the tumor, reducing the risk of damage to healthy tissue. It can be used to treat many cancers. At Mayo, brachytherapy is used to treat patients with prostate, gynecologic (cervical and endometrial), biliary and lung cancers and soft tissue sarcomas. Brachytherapy can be either a permanent implant or temporary implant (placement) of radioactive material.
In permanent brachytherapy, several dozen tiny radioactive seeds are placed in a tumor under the guidance of ultrasound, CT or MR scans and are left in place. The seeds give off low doses of radiation for weeks or months. The seeds may be placed during surgery or in a separate procedure. Patients are sedated and given pain medication but do not need deep anesthesia and are thus not hospitalized. Permanent implants are used for prostate cancer (see below) as either the total treatment or as a supplement to external beam radiation (EBRT).
Temporary brachytherapy implants may be used as a supplement to EBRT for patients with gynecologic, biliary or lung cancers and for soft tissue sarcomas. For patients with soft tissue sarcomas and select lung cancers, after the patient's cancer is surgically removed, hollow tubes may be placed in the surgical bed (location of the initial cancer). The catheters serve as a conduit for temporary placement of low-dose-rate (LDR) brachytherapy seeds that are imbedded in plastic strands. The brachytherapy seeds are usually left in position for 30-50 hours, and then both the seeds and catheters are removed.
Read more about brachytherapy treatment at Mayo Clinic.
For selected patients with early low risk prostate cancer, implanting the gland with radioactive "seeds" is an effective treatment option. Performed as outpatient surgery, the procedure allows the patient to return to normal activity the next day. Additionally, it may in many instances negate the need for 8-9 weeks of external beam radiation (EBRT). The risk of severe complications is low, and the long-term results quite favorable compared to other treatment options (surgical removal, EBRT). The staff at Mayo has performed over 1,000 prostate seed implants during the past 15 years.
Further information on the treatment of early prostate cancer can be found in an Early-Stage Prostate Cancer Health Decision Guide.
Read more about permanent prostate brachytherapy at Mayo Clinic.
Stereotactic radiosurgery uses precisely focused radiation to treat tumors and other abnormal growths in the brain. Computers create 3-D images of the brain, and these images guide radiation oncologists and surgeons in aiming radiation from many sources at the target area. The technology allows high doses of radiation to be delivered to the tumor with minimal exposure to surrounding healthy tissue. No incision is made and general anesthesia is not required for adults. In effect, it is surgery without a scalpel.
Read more about stereotactic radiosurgery at Mayo Clinic.
Many patients undergoing bone marrow transplantation first receive a course of total body irradiation in order to help destroy the cancer cells in the marrow and elsewhere. Delivering an acceptably uniform dose over the entire body requires special dose measurements and treatment techniques. This therapy is generally used for patients with specific types of leukemia or lymphoma.
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