Stereotactic Radiosurgery May Pose Radiation Overdose Risk

Stereotactic radiosurgery, a fast growing cancer therapy that utilizes high intensity, pinpoint radiation, could be putting patients at significant risk, according to The New York Times. In fact, the Times investigation found that over the past five years, <"">linear accelerators made by Varian Medical Systems, and its partner, Brainlab, have figured in scores of errors and overdoses during stereotactic radiosurgery therapy. In many cases, patients sustained severe, life-altering injuries.

Stereotactic radiosurgery is designed to target tiny tumors and other anomalies affecting the brain or spinal cord, while minimizing damage to surrounding tissue. According to the Times, because the amount of radiation utilized by such procedures is concentrated and intense, accuracy is important.

Stereotactic radiosurgery procedures often use linear accelerators that have been modified for that purpose. Such a system made by Varian and Brainlab was used in three identical stereotactic radiosurgery procedures that resulted in radiation overdoses at Illinois’ Evanston Hospital, according to the Times. In those cases, the device had inexplicably allowed radiation to spill outside a heavy metal cone attachment that was supposed to channel the beam to a specific spot in the brain. In one of the Evanston cases, a patient was left comatose and now resides in a nursing home. The chairman of radiation medicine at Evanston told the Times that the mistakes occurred even though medical personnel there had followed the manufacturer’s instructions.

According to the Times, the linear accelerator involved in the Evanston overdoses was used for standard radiation therapy, but redesigned by Varian for use in stereotactic radiosurgery. “As the devices became more versatile and complex, problems arose when vital electronic components could not communicate with one another,” the Times said.

According to the Times, stereotactic radiosurgery systems made by Varian have been implicated in similar mishaps. For example, 76 patients were overradiated in Missouri because a medical physicist did not realize that the smaller radiation beam used in radiosurgery had to be calibrated differently than the larger beam used for more traditional radiation therapy.

Medical experts told the Times that such problems likely result from several factors. For example, Dr. Howard I. Amols, chief of clinical physics at Memorial Sloan-Kettering Cancer Center in New York, said that they appear to be “a combination of user error, coupled with neither the manufacturers nor the FDA (Food & Drug Administration) being able to anticipate a potential safety flaw in a ‘mix and match’ treatment delivery system.”

According to the Times, mistakes involving stereotactic radiosurgery systems highlight shortcomings in the regulation of medical radiation. For one thing, such multipurpose devices are less regulated than their more simply designed competitor, the Gamma Knife, a device engineered specifically for stereotactic radiosurgery. Linear accelerators, because they do not use nuclear material, are regulated by the FDA, while the Gamma Knife – which uses a radioactive isotope – falls under the jurisdiction of the Nuclear Regulatory Commission. Retrofitted linear accelerators were approved by the FDA with little review on the grounds that they were mere extensions of existing technology, the Times said.

There is no requirement that all mistakes involving linear accelerators be reported to a central database, the Times said, so there is no way of knowing how often such incidents occur.

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