Melbourne Internal Medicine Associates (MIMA) Treats Metastatic Cancer Using Ultra-Precise Image-Guided Radiotherapy Technology From Varian Medical Systems.
The 64-year-old male patient had been treated a year earlier for lung cancer, along with a solitary brain metastasis. He subsequently lived for almost a year with no sign of cancer, according to Todd Scarbrough, MD, radiation oncologist and director of the MIMA Cancer Center. Then, in a routine surveillance scan, MIMA radiologists spotted a metastatic lesion in the patient's liver.
"We had three choices," Scarbrough said. "We could do nothing. We could treat him with chemotherapy. Or we could use our new image-guided radiotherapy technology to deliver a very high dose of radiation directly to the tumor in what's known as a 'radiosurgical' treatment. With radiosurgery, we deliver very high doses of radiation in just one or a few treatment sessions. This requires us to target the lesion very precisely, compensate for any tumor motion, and do all we can to protect the surrounding healthy tissues."
In the past, radiosurgical procedures have been used primarily to treat tumors in the brain, because the head can be effectively immobilized, which renders brain tumors motionless and facilitates accurate targeting. "Body radiosurgery is a new procedure, made possible by technologies like the On-Board Imager®, which helps us ensure that our treatment beams accurately hit the tumor," Scarbrough said.
To position their patient for treatment, Scarbrough and his clinical team utilized two of the imaging modalities available with the On-Board Imager: radiographic kV X-ray imaging, and three-dimensional cone-beam CT imaging.
"Prior to each treatment, we used the On-Board Imager to take orthogonal X-ray images of the liver and used them to calculate how to shift the patient to make sure the tumor was lined up precisely with the treatment beam," Scarbrough said. "We were amazed at how well the liver showed up on the radiographic X-ray images. We could see enough detail to make the necessary positioning corrections. We then generated a three-dimensional cone-beam CT image as a check, to verify that our calculations were correct in all three dimensions."
To address the problem of tumor motion due to respiration, MIMA clinicians used a CT scanner outfitted with Varian's RPM™ respiratory gating technology to generate the images used in treatment planning. "This enabled us to choose the optimal point in the patient's respiratory cycle for delivering each treatment," said Joseph Ting, PhD, chief medical physicist at the MIMA Cancer Center.
The novel radiosurgical procedure involved three treatments delivered every other day over a five-day period.
"Our goal was to see if we could eradicate the liver lesion using a method that has essentially zero toxicity, sparing him the more toxic effects of chemotherapy," Scarbrough said. "The treatment was administered four weeks ago. The patient is doing great and has suffered no side effects. A CT scan in early March showed that the liver lesion had regressed dramatically. It is too early to say what the long-term results will be, but we're very hopeful."
Virtually all cancer patients treated with conformal radiation therapy at MIMA now receive image-guided treatments. "We use every tool at our disposal to set up the patient more accurately for treatment," said Ting. "With IGRT, we are very confident we're targeting the right place."
