Melbourne Internal Medical Associates (MIMA) Cancer Center in Florida announced that its doctors have treated a metastatic liver tumor using MIMA’s IGRT (with image-guided radiotherapy) system equipped with Varian's On-Board Imager device for positioning patients with sub-millimeter accuracy.
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, said 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. 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," said Scarbrough. "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.
Scarbrough and his clinical team utilized two of the imaging modalities available with the On-Board Imager to position the patient: 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," said Scarbrough. "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," he added.
To address tumor motion, MIMA clinicians used a CT scanner outfitted with Varian's RPM respiratory gating technology to generate the images used in treatment planning.
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," said Scarbrough. "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," he added.