UPMC uses Varian system to treat tumors in motion
Clinicians at the University of Pittsburgh Medical Center (UPMC) Cancer Centers recently successfully treated a lung cancer patient in her mid-fifties using a new technique that combines image-guided radiotherapy (IGRT) with respiratory gating to focus on a tumor with the ability to adapting for breathing motion. The procedure was done using Varian Medical Systems’ Trilogy linear accelerator advanced imaging and treatment technology.
The UPMC medical team custom designed the treatment to protect the patient’s heart and esophagus as well as the healthy parts of her lung. The Dynamic Targeting IGRT treatment was delivered using the linear accelerator equipped with an On-Board Imager for monitoring tumor motion and the RPM 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, MD, 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."
This procedure did not produce quite the same side effects -- including inflammation of the esophagus or healthy lung tissue -- that are seen in usual cancer treatments, Varian said.
To position the patient for treatment each day, the UPMC clinical team made use of the On-Board Imager to generate radiographic x-ray images of the targeted area prior to each treatment session. With the push of a button, the patient was then repositioned, based on changes detected in the daily images.
An imaging study of the patient revealed that her tumor moved 1.2 centimeters each time she took a breath. Often, tumor motion of this magnitude would require the treatment of an additional margin of about 1 to 1.5 centimeters around the tumor, in order to ensure that the treatments fully encompassed the tumor. In this patient's case, the RPM respiratory gating technology helped the team solve the problem without having to treat any additional areas.