As reported by the New Haven Register, December 17, 2007.

New Cancer Blasting Device Can Pinpoint Tumors

By Abram Katz

Killing cancer cells is easy.

Killing them without damaging or destroying healthy tissue is a challenge that oncologists have been working on for decades.

Scientists are working on new chemotherapy agents that promise to target only errant cells, while engineers develop ever more precise ways to deliver radiation.

Cancer centers are now adopting a new nine-ton piece of equipment that delivers X-rays with unparalleled accuracy, allowing doctors to use higher doses of radiation to wipe out certain cancers without irradiating adjacent organs.

Image Guided Radiation Therapy, or IGRT, permits doctors to blast tumors with extraordinary accuracy.

"This represents an evolutionary change in radiation therapy," said Dr. Daniel E. Fass, director of radiation oncology at Greenwich Hospital.

Greenwich Hospital and the University of Connecticut Health Center in Farmington are among the growing number of hospitals using the TomoTherapy Hi-Art system developed by TomoTherapy Inc. of Madison, Wisc.

Several other companies also make IGRT systems.

About 15 to 20 years ago, Intensity Modulated Radiation Therapy was the cutting edge, Fass said.

Using CT scans and an X-ray with a computer-controlled set of tungsten leaves, the radiation could be restricted to a smaller area. The multi-leaf collimator could also be rotated around the patient to direct beams from other directions.

One of the improvements in image guided radiation therapy is the combination of X-ray and CT scan.

In the TomoTherapy equipment, one accelerator provides the X-rays for both the scan, which shows the exact location of the tumor, and the treatment. A much less intense beam is for the CT scan.

This assembly is programmed to rotate within an O-shaped housing as a table carrying the patient advances through the hole slowly.

"This requires a big rack of computers," Fass said. The computers coordinate the X-ray dosage, the rotation of the beam, the intensity of the beam, and the speed of the table.

By incorporating the CT scan into the machine, oncologists are able to re-aim the beam to within 2 millimeters before treatment starts.

This is important because organs and tumors are not locked in place. They move between treatments.

Added precision means the X-ray beam can be smaller. This reduces the energy, but exposure can be lengthened because the x-rays are not impinging on surrounding tissue, Fass said.

For example, a prostate can be irradiated without damaging the rectum, or the head can be treated without destroying salivary glands. Because the X-ray beam moves in a helix, the radiation is spread sufficiently so no single area sustains too much damage.

X-rays kill cancer by blasting apart DNA within the tumor. DNA damage prevents the cell from dividing. Chemotherapy drugs also attack DNA, which is why they are effective against rapidly-dividing cells. However, the agents also attack other, normal cells that grow quickly, such as hair, cells that line the intestine and bone marrow.

IGRT avoids these kinds of side effects.

"IGRT studies are promising. There is improved survival with higher doses of radiation," Fass said.

"While there is a five-year requirement to measure success, we anticipate a cure rate in the range of 90 to 95 percent for prostate patients with this new, more advanced technology," he said.

Side effects are markedly reduced, he said. Tumors are typically treated for six weeks.

IGRT is suitable for solid tumors in the brain, head and neck, and lungs. It is also ideal for prostate and gynecological tumors, he said.

"We looked at several options and concluded that this state of the art system is clearly a step above other radiation technologies and wanted to make it available to residents of Connecticut and the region," said Dr. Carolyn D. Runowicz, director of the Neag Comprehensive Cancer Center at the UConn Health Center.

Dr. Robert Dowsett, director of the center’s division of radiation oncology said the treatment involves several steps.

Before each treatment the patient is moved through the Hi-Art machine for a CT scan. Images verify the shape, size, and location of the tumor.

The CT scan image is then compared to the original CT scan image, which may have been taken several days before. Fass said he prefers a "dry" run-through with film to confirm the positioning of the patient and other parameters.

Fass said the TomoTherapy machines are being sold as rapidly as they can be made.

"In a few years they will be commonplace," he said.

Because the machine weighs 18,000 pounds, it cannot be casually placed in an unused room. The room must also be shielded so that X-rays do not escape.

Consequently, hospitals and medical centers would need to construct a space with special walls and a floor to house the apparatus.