Trilogy: Targeting Cancer As Never Before
 
Andrew L. Salner, M.D.
The Trilogy™ Stereotactic System from Varian Medical Systems at the Helen & Harry Gray Cancer Center is the first of its kind in Connecticut. 
 
The hospital is building on its reputation as a leader in radiation oncology with this versatile new image-guided radiation therapy (IGRT) system. Trilogy’s “dynamic targeting” assures accurate beam positioning, while built-in CT (“cat scan”) diagnostic imaging pinpoints tumors with digital accuracy  and positions them in the high-dose area despite any internal organ movement. Advances in low-dose, high resolution X-ray imaging, precision delivery and patient positioning are the three advantages of the Trilogy system.
 
In addition to image guidance, the other two components of the unique triad are intensity modulated radiation therapy and stereotactic radiation therapy.
 
Since 2003, radiation oncologists at the Cancer Center have used intensity-modulated radiation therapy (IMRT) to “shape” a dose of radiation to match the contours of a specific tumor.
 
“We can superimpose thousands of small fields of radiation to sculpt the beam around a solid tumor,” says Andrew L. Salner, M.D., director of Hartford Hospital’s Cancer Program. “The prostate gland tends to move within the body, so we image the tumor before treatment every day.”

Not only is the next-generation Trilogy linear accelerator safer and more sophisticated than existing systems, it adds new options for stereotactic neurosurgical treatment. With the Trilogy system, radiation oncologists and their neurosurgical colleagues can target inoperable lesions or tumors in critical
areas of the brain, using image-guided delivery and a helmet-like device that holds a patient’s head completely still during radiosurgery."
 
We can now deliver a precisely placed, one-shot or multi-shot, extremely high dose of radiation to a tumor in the brain,” says Dr. Salner. “The beam is so highly focused that sensitive structures like the optic nerve receive significantly less radiation.”
 
 Even more precise than so-called “gamma knife” radiosurgery, the state of-the-art Trilogy system minimizes radiation damage to healthy tissue. Hartford Hospital’s Radiation Oncology Department also offers brachytherapy—either permanent or temporary—for prostate cancer treatment. Permanent seed implants can be implanted into the prostate gland, where they give off radiation at a low dose rate over several weeks or months.
 
“Temporary brachytherapy can be targeted much more precisely to spare the urethra,” explains Dr. Salner. “Tiny catheters deliver highly radioactive iridium-192 seeds to the tumor. Because the computer controls how long each seed remains in each catheter—from fractions of a second up to many seconds—we can selectively control he radiation dose to different regions of the prostate.” The hospital’s prostate ancer team individualizes care for each patient and helps to determine which option is best for each patient.

Brachytherapy is also used in the management of several other types of cancer. For example, women with localized breast cancer who meet specific criteria are candidates for MammoSite partial breast radiation, which can be completed in five treatment days instead of the usual six weeks. The technique utilizes high dose rate brachytherapy consisting of a twice daily 20-minute treatment to focus on the portion of the breast at risk.
 
Radiation oncologists are now collaborating with medical oncologists/hematologists to bring new approaches to cancer treatment. Hartford Hospital is pioneering a radioactive cancer breakthrough called radioimmunotherapy. To deliver a dose of radiation to a tumor target, radiotherapy drugs hitch a ride on a monoclonal antibody —a protein designed to lock onto a specific area on a cell’s surface.
 
Once they acquire their molecular target, yttrium-90 or iodine-131 radioisotopes blast the cancer cell with a lethal dose of radioactivity. The FDA has approved two radioactive drugs, Zevalin and Bexxar, for patients with relapsed or recurrent Non-Hodgkin’s lymphoma who have failed chemotherapy.