Lung cancer remains the number one cancer killer, and its five-year survival rate of less than 15 percent has hardly budged over the last 30 years, according to the U.S. National Cancer Institute. But new Varian technology, “respiratory gating,” offers patients and doctors the hope of more aggressive and successful treatments.

Respiratory gating makes it possible to track the position of tumors that move as much as 4 centimeters (more than 1.5 inches) as the patient breathes. Varian’s RPM™ gating system—now in place at more than 300 cancer centers around the world—uses an infrared camera and a special marker placed on the patient’s diaphragm. Breathing can be monitored while taking CT scans for treatment planning as well as during treatment sessions, allowing doctors to pick the best moment in a patient’s breathing cycle to turn on the beam. As a result, the margin of treatment around the tumor can be significantly reduced and the total dose can be increased without fear of harming the surrounding normal tissue.

“Traditionally we used margins of anywhere from 3 to 5 centimeters around a tumor to ensure that we were getting adequate coverage,” says Anthony Berson, MD, chair of the Radiation Oncology Department at St. Vincent’s Comprehensive Cancer Center in New York. With respiratory gating, the margin has been reduced to 1 to 2 centimeters. “That’s a huge improvement.”

At the same time, the total dose can be increased. “Our initial goal is to increase the dose 10 to 20 percent,” says Berson. “It’s too early to see what the long-term results are, but we expect that as we increase the dose, we should be controlling tumors at a higher rate.”

At the Marin Cancer Institute in Greenbrae, California, Francine Halberg, MD, has been using respiratory gating to treat left-sided breast cancer, where the ability to precisely target a tumor helps avoid irradiating heart tissue and prevent related side effects. Respiratory gating protocols for lung cancer “usually seek to deliver treatment at the point of the patient’s maximum exhalation,” says Halberg. “That’s a very stable point, and very consistent relative to other parts of the breathing cycle. However, for treating breast cancer, we’re looking for the farthest inhalation because that’s when the breast moves furthest from the heart.”

Halberg has treated more than two dozen breast cancer patients with respiratory gating after their tumors were removed by lumpectomy. “We have a very, very low risk of recurrence after radiation therapy to the breast,” she says.

At St. Vincent’s, more than 300 patients have been treated with respiratory gating over the last three years. In addition to lung cancer, Berson and his team have used respiratory gating to treat upper abdominal cancers, including pancreatic, stomach, and liver tumors, which also move as patients breathe. In those cases, Berson says, the large radiation fields required by traditional techniques, combined with chemotherapy, result in high complication rates. “In that situation,” he says, “anything you can do to reduce the size of the field will reduce unwanted complications.”

The significant improvements respiratory gating makes possible can be achieved easily, without disrupting a clinic’s practices. “We are a very busy community hospital, and our throughput is very high,” says Berson. “We see a lot of patients in a day. This is just a normal part of our day.”

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