Radiation therapy for cancer gets on the beam


Radiation therapy, a treatment for cancer more than a century old, has become much more powerful and precise with the help of the computer. Harmful side effects of radiation on normal tissue have been lessened, and tumors once untreatable by radiation can now be reached.

Two relatively new technologies, called the CyberKnife and intensity modulated radiation therapy (IMRT) , make plentiful use of computing power and precise medical imaging to determine the tumor location. The details of how they work are different, but both deliver X-ray radiation in a concentrated pattern from many directions that converge at the tumor.

The concept resembles that of another targeted radiation therapy, called the Gamma Knife, which sends about 200 beams of gamma radiation into the tumor. But while the Gamma Knife can be used only for lesions of the brain, the CyberKnife and IMRT can be used over the entire body.

IMRT and the CyberKnife are "complementary," said Cihat Ozhasoglu, a medical physicist at the University of Pittsburgh Medical Center. The CyberKnife, the newer of the two therapies, is more precise in delivering radiation. But IMRT is superior for treating large and irregular tumors.

Because radiation damage to normal tissue is lessened, both treatments cause less fatigue in patients, a common side effect of radiation, than in conventional radiation.

"It's much more pleasant than I thought it would be," said Eugene Fundum, a Temecula resident who received IMRT for prostate cancer. Fundum, 76, was treated at the Vantage Oncology Redhawk Radiation Therapy Center, which opened earlier this year in Temecula.

Earle Grueskin took CyberKnife therapy at the San Diego CyberKnife center in Kearny Mesa. Grueskin is also 76 and also has prostate cancer.

"There was absolutely no pain before, during or after the treatments," Grueskin said.

Both Fundum and Grueskin said their levels of PSA (prostate specific antigen, an indicator for prostate cancer), have declined dramatically since their treatment in July. They'll need periodic checkups to check for tumor regrowth.


The name gives a good indication of how intensity modulated radiation therapy works. It delivers patterns of radiation that vary in intensity. That's important because certain parts of the body are more sensitive to radiation than others. The prostate, for example, is located between the bladder and rectum. Radiation to these organs must be controlled to avoid damaging bladder and bowel function.

First, the patient is given a CT scan to map the area, so the staff can plan the treatment. A CT scan is a series of X-rays, each focused to show a sharp image of adjacent thin slices of the area. These are digitally combined in a computer to form a 3-D image. This shows where the tumor is in the patient.

That's not enough, however. The patient's position must be tracked so if he or she moves, the radiation's path also moves. An ultrasound guidance system called SonArray provides that information, said Mary Ann Rose, M.D., a radiation oncologist who is medical director of Redhawk Radiation Therapy Center and Wildomar Radiation Therapy Center. The centers, owned by Vantage Oncology, provide a variety of other radiation therapies.


