The advantage of the treatment, called neutron brachytherapy, is that physicians can deliver a highly concentrated dose of californium-252 neutrons to the site of a tumor instead of having to treat the tumor with conventional gamma rays, which often are not as effective. This therapy has proved particularly useful against cancers that are resistant to photon and gamma treatments, which do not kill cancer cells as effectively as do the californium-252 neutrons.
Cancers most resistant to the conventional treatments include brain tumors, melanoma, sarcoma, certain types of prostate cancer, locally advanced breast cancer, cervical cancer and cancer of the head, neck and mouth.
“The progress achieved with neutron brachytherapy will enable unprecedented cancer treatment and will help physicians treat nearly 20 different types of cancer,” said co-developer Rodger Martin of ORNL’s Nuclear Science and Technology Division.
The key to the ORNL success is the miniaturization of the californium-252 source, which allows physicians to insert the radioisotope through a catheter directly to the tumor site.
Martin and colleagues were able to reduce the diameter of the source by more than half from the previous standard of about 2.8 millimeters. This makes it possible to reach and treat tumors that previously could only be treated with conventional photon and gamma brachytherapy or with external beam treatments. ORNL and Isotron’s success is the result of many months of development and testing that began in 1999 with the signing of a three-year cooperative research and development agreement.
After reducing the diameter of the source -– the wire that contains the radioisotope -- Martin and colleagues at Isotron faced the engineering and fabrication challenge of developing a method of attaching the capsule to a positioning cable that would allow medical personnel to deliver the radiation dose to the target. Next, the ORNL team modified a commercial welding system for miniature capsules and overcame several other fabrication challenges that ultimately allowed them to produce the miniature sources in hot cells that shield operators from the radiation.
“Our system combines the miniature high-activity neutron sources with a remote, automated storage and delivery system that utilizes the latest imaging, surgical and patient treatment planning techniques,” said Steve Jacobs, acting chief executive officer of Isotron.
Martin and Jacobs envision their treatment being useful for treating many of the some 257,000 combined cases of prostate cancer, cervical cancer, brain tumors and melanomas that claimed 64,700 lives in 1998. They’re especially encouraged about the prospects of their treatment helping patients with glioblastoma multiforme, the most common primary brain tumor. It is extremely resistant to conventional forms of treatment; the five-year survival rate is less than 1 percent.
ORNL is a DOE multiprogram research facility managed by UT-Battelle.