Novel Radiotherapy for Lung Cancer Targets Moving Tumors

Clinicians have successfully treated a lung cancer patient using a more precise technique that combines image-guided radiotherapy (IGRT) with respiratory gating to narrow in on the tumor while adapting for breathing motion.

The tissue-sparing procedure, performed by clinicians at the University of Pittsburgh Medical Center (UPMC; Pittsburgh, USA) Cancer Centers, was made possible using sophisticated imaging and treatment technology from Varian Medical Systems (Palo Alto, CA, USA). The UPMC medical team specially designed the patient's treatment to protect the heart and esophagus as well as the healthy parts of the lung.

The Dynamic Targeting IGRT treatment was delivered using Varian's Trilogy linear accelerator equipped with an On-Board Imager for monitoring tumor motion and the RPM (real-time position management) respiratory gating system for synchronizing beam delivery with the patient's natural breathing cycle.

"We had to be concerned about compromising this patient's ability to breathe,” said Dwight Heron, M.D., vice chairman of clinical affairs, department of radiation oncology, UPMC Cancer Centers. "As a result, it was vitally important to minimize the exposure of radiation to the surrounding healthy lung tissue.”

An imaging study of the patient, who was in her mid-50s, revealed that her tumor moved 1.2 cm with every breath she took. Conventionally, according to Dr. Heron, tumor motion of this magnitude would have required him to treat an additional margin of about 1-1.5 cm around the tumor, to ensure that the treatments fully encompassed the tumor. In this patient's case, he felt that this would have meant irradiating too large a volume of healthy tissue in the upper lobe of her left lung.

"We set our RPM respiratory gating system to deliver the treatment beam only during a particular part of her respiratory cycle, when her tumor moved the least,” Dr. Heron said. "This happened when she was about halfway through her exhalation--the tumor was virtually motionless at that point, so we could target it very accurately. Using this approach, we were able to decrease the treatment margin to half a centimeter.

"Up to now, most early stage lung cancer patients have been treated with chemotherapy or surgery--very few received radiation, because accurate targeting was difficult to achieve,” said Dow Wilson, president of Varian's Oncology Systems business.



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University of Pittsburgh Medical Center
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