IG-IMRT: Treating Cancer Like Never Before

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The Siemens ONCOR linear accelerator, in use at the Baton Rouge General Radiation Oncology Center in Baton Rouge, La.,  integrates technologies for planning, simulating, delivering and verifying treatment.

Intensity modulated radiation therapy (IMRT) continues to gain popularity and now more facilities are turning to image-guided radiation therapy (IGRT) for even more precise treatment of several forms of cancer. Even as the two technologies are the on the leading edge for cancer treatment, further developments are underway. In the near future, adaptive treatment will let radiation oncologists adjust treatment on a daily basis, if necessary.

“IMRT has certainly stayed its course and proven itself,” says Arno Mundt, MD, professor and chairman of the radiation and oncology department at the University of California at San Diego. “IGRT is the new kid on the block. It’s the rave of a lot of vendors.”

These new technologies take advantage of a broad range of expertise, says Todd Pawlicki, PhD, medical physicist and Mundt’s colleague. IMRT and IGRT “will allow us to treat some tumors in a way we were never able to treat before—much more accurately, conformally, and with higher doses to the target while still sparing normal tissue nearby. It’s a quantum step. It’s transforming the whole field.”

The team uses a Trilogy linear accelerator from Varian Medical Systems. In-room imaging, using a range of sophisticated technologies, is becoming more and more popular, Mundt says. Plain x-ray films through mounted imagers on the machine guide clinicians, sometimes even during treatment. “Pre-IGRT, we were only able to verify a patient’s position on a weekly basis,” says Pawlicki. “Now, with IGRT for localization, we’re able to actually localize and verify the patient’s position and adjust daily, if necessary.”

Current efforts will lead to real-time adaptive therapy—“the pinnacle for individualized medicine,” says Pawlicki. Adaptive treatment is one of the most important new developments, says Mundt. By imaging the tumor every day to see any changes, clinicians can adapt their treatment efforts accordingly. “That’s a very cutting-edge concept that still needs to be worked out. That’s going to be a paradigm shift in how we treat patients.”

A researcher working with Mundt is looking at adaptive treatment for gynecological tumors. Cervical tumors shrink very rapidly when treated and the uterus can be in a different position every day so gynecological tumors’ response to adaptive treatment is of particular interest. Although adaptive treatment is strictly a research endeavor at this point, Mundt hopes to see it come into practice use within the next couple of years. “We can taste it,” he says.

Increased use of IMRT and IGRT requires “education, education, education,” says Pawlicki. “As a general goal, we need to raise the level of understanding of these technologies throughout the field and how to complement them correctly.” An experience base and an understanding of how to implement accurately and safely is a challenge for the field, Pawlicki says.

More routine offering

Jerome Landry, MD, radiation oncologist at Emory Winship Cancer Institute in Atlanta, Ga., is another early adopter of IGRT technology, having worked with it for about four years. He uses both the Clinic and Trilogy linear accelerators from Varian Medical Systems, equipped with the On-Board Imager for IGRT. “When we began, there wasn’t a lot of clinical experience throughout the country.” Although Landry was originally using the technology in a research mode, he has since used it for pancreatic, prostate and gastrointestinal cancers, and head, neck and brain tumors. “As people started publishing on the side effects, we started offering it more routinely.”

At first, integrating IGRT into the treatment paradigm added an extra 15 to 20 minutes to a 30-minute patient time slot. Once IGRT was integrated for daily set up tracking, Landry worked on clinical efficiency. At first, both therapists and clinicians were at the treatment console and were aligning the patients, using manual matching. The doctors wanted to see all the patients and all of the daily changes the therapists made. They got to a point where they could calculate the average maximum shifts during treatment and gave the therapists parameters. If the shift was less than a certain amount for a certain type of tumor, they could make the shift without referring to the doctor. That extra 15 to 20 minutes was eventually