Glioblastoma multiforme after microsurgery for acoustic neuroma without radiotherapy: limitations of the Cahan criteria.

In 1948 Cahan and others reported 11 cases of sarcoma that arose in radiated bone, mostly in children treated for tuberculosis. They studied only cases that met certain inclusion criteria: 1) there must have been histologic or radiographic evidence of the nonmalignant nature of the initial condition; 2) the sarcoma that arose must have arisen in the area included in the radiotherapeutic beam; 3) there must have been a relatively long, asymptomatic period of latency between radiation and development of the sarcoma; and 4) the sarcoma must be proved histologically. Since Cahan’s report, these criteria have often been cited as requirements for considering a case to represent radiationinduced malignancy. Since the 1980s there has been considerable interest in stereotactic radiosurgery and other forms of focused radiation therapy for nonmalignant conditions. One of the concerns raised by radiation treatments for acoustic neuroma, which has somewhat limited their use, is the potential for radiation to induce other intracranial tumors, including malignancies. Because such cases are rare, it has been difficult to establish a reliable estimate of their occurrence to guide selection of treatment and patient counseling. We report a case that we feel should be taken into consideration when estimating the risk of radiation-induced malignancy. Institutional Review Board approval was obtained. A 58-year-old woman presented to the emergency department complaining of increasing ataxia for the past two weeks. She also noted numbness and tingling in the right face and body, diplopia, blurred vision, nausea, and vomiting for the same period. On the morning of admission she experienced a severe pressure headache at the right mastoid process, which spread to include the left side within a few hours. The past medical history was significant for microsurgical excision of a right acoustic neuroma two years previously. This was conducted as a two-stage procedure at another center. A few months postoperatively she received an osseointegrated implant for single-sided deafness. The patient’s family history was negative for cancer, schwan-