TomoTherapy offers safer radiation

CorrespondentJanuary 30, 2012 

Radiation therapy, once considered a crude weapon of last resort in the war on cancer, has gotten so sophisticated, oncologists joke its latest version involves "bending a beam."

That's, of course, an exaggeration of what a TomoTherapy machine really does.

TomoTherapy treatment promises radiation therapy that damages less healthy tissue surrounding some of the most challenging tumors - those that are odd-shaped or curve inward, particularly in the head, the neck and the pelvic area.

"It has more degrees of freedom, so you have more customization," said Dr. Larry Marks, who heads the radiation oncology department at the UNC School of Medicine. "It enables you to do unusual stuff."

Three hospitals in North Carolina have a TomoTherapy machine. Moses Cone installed the first in 2009 at its Regional Cancer Center in Greensboro. UNC Health Care followed suit about half a year ago, with a machine each at Rex Hospital in Raleigh and at UNC Cancer Care in Chapel Hill - the clinical home of the UNC Lineberger Comprehensive Cancer Center.

Cancer researchers began using the energy from radiation to kill out-of-control tumor cells about 100 years ago, but surgery remained the preferred cancer treatment until after World War II. Machines that produced high-energy beams for cancer treatment were introduced in the 1950s, including the first medical linear accelerator X-ray machine. In the 1970s, computers began to enable oncologists to scan a body and pinpoint a cancerous growth for radiation.

Three-dimensional radiation therapy is one of the most commonly used methods to kill cancer from outside the body, according to the National Cancer Institute. Doctors use a computer to create a three-dimensional image of the tumor and expose it to the highest possible dose of radiation. The machine to administer the dose is usually a medical linear accelerator.

Linear accelerators can also be used for intensity-modulated therapy, which exposes parts of a tumor and nearby healthy tissue to different doses of radiation. A TomoTherapy machine is less geometrically challenged. Shaped like a donut, it can generate beams from 51 different angles, compared to the nine angles a linear accelerator manages without the patient having to move, and a TomoTherapy machine has 120 lead leaves to further block areas from exposure. This ability to customize is what promises to spare more healthy tissue and reduce side effects, particularly in cases of cervical, prostate and oral cancers and cancer in the voice box.

To further reduce potential side effects, which range from skin irritation and diarrhea to infertility and cancers caused by the radiation treatment itself, UNC researchers have teamed up with researchers at Duke University, Marks said. Together, they are studying whether lower radiation doses on a TomoTherapy machine can produce the same result as higher doses on a linear accelerator.

Sabine.vollmer.reporter@gmail.com

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