INNOVATOR: RADIATION ONCOLOGY
When a lung-cancer patient goes to the hospital for radiation therapy, he doesn’t need the treatment to zap his heart or spinal cord, though that may be just what happens. The inexact science of radiation oncology requires doctors to point an external beam of accelerated electrons at dots on the skin marking the internal location of a tumor. Since the lung moves when a patient breathes, standard protocol is to treat an area fifteen times the volume of the tumor, an area that includes healthy lung tissue, and sometimes healthy, unrelated organs.
The main reason for the wide margin of error is a disconnect between the CT imaging used to locate the tumor and the LINAC (linear accelerator) radiation used to treat it. Typically, doctors take CT scans days before treatment, then mark the skin for a four-to-eight-week course of therapy. Once a week, the doctor uses the LINAC to take what look like blurry X-rays to recheck his aim, but as James Wong, chief of radiation oncology at Morristown Memorial Hospital in New Jersey, points out, “It’s like you take a doctor with 20/200 vision, allow him to see the tumor and the critical organ in one shot, and then throughout the eight weeks of radiation you take away his glasses.”
Working with the Siemens corporation, Wong has developed the country’s first CT-image-guided radiation machine, which allows imaging and treatment in the same room, on the same bed, at the same time. The concept, originally developed in Japan by Wong’s friend Minoru Uematsu, simply combines two previously FDA-approved devices. Instead of the patient lying on a bed that goes through the CT scanner, then switching to the LINAC table in another room at another time, a specially designed CT scanner moves over the LINAC table; the patient never moves. “Because we know the exact location of the tumor,” says Wong, “we can make the entry area smaller, thus avoiding critical normal tissue that might otherwise be hit.”
All organs can take a certain amount of radiation, says Wong, but then you reach a threshold. “With the spinal cord, the patient has a chance to be paralyzed. With the heart, you could go into heart failure. With lungs, the patient can become a pulmonary cripple.”
Because of that risk, conventional therapy requires lower doses of radiation over a larger number of treatments. Wong’s technique, meanwhile, allows him to administer higher-intensity radiation over fewer treatments.
In a seven-year study of Stage I lung cancer, Wong and Uematsu have shown that high, concentrated doses of radiation can kill tumors and prevent recurrence at the same rate as surgery. Wong’s studies also showed that a high-intensity protocol killed or limited the growth of tumors in 80 to 90 percent of cases—compared with a 20 to 30 percent rate for conventional radiation. And with high-intensity radiation, Wong adds, “no patients had deterioration of pulmonary function.”
So far, Wong has used his machine mainly on prostate and lung cancers. Other major cancer centers, however, like M.D. Anderson in Houston, have begun using the device to treat tumors near the spinal cord. The next step? “The brain,” says Wong. “Where every millimeter counts.”