Doctors are treating eye tumors at a UC Davis lab cyclotron built for nuclear physics, but now equipped to handle outpatient eye therapy. Cancer patients come from as far away as New Zealand and as close as Palo Alto to the UC Davis Crocker Nuclear Lab, referred from UC San Francisco's Ocular Oncology unit. Treatment facilities such as that at the Crocker Lab are unusual, with only about a dozen worldwide, and only a few of those in the United States. "The frequency of the tumor is so rare only 2,500 patients are diagnosed annually in the U.S.," says Dr. Joseph Castro, a UC physician who treats such patients using the UC Davis cyclotron. The lab uses a specialized proton radiation beam. "The advantage of this beam is that it can be focused and brought into the eye and stopped at a specific depth. It's a proton particle beam, not an X-ray beam." Although the procedure preserves the eye 90 percent of the time, saving a patient's vision is often less successful, Castro says, because the tumor is often so close to the optic nerve. The treatment had been conducted for 15 years at the Lawrence Berkeley Lab, but recently was shifted to UC Davis.