Analysis of Toxicity in Patients with Collagen Vascular Diseases or Multiple Sclerosis Treated with Gamma Knife Radiosurgery for Intracranial Tumors

Previous series have suggested a possible increased rate of toxicity in patients with collagen vascular disease receiving radiotherapy, and with patients with multiple sclerosis receiving brain irradiation. We aimed to assess toxicity in patients with these cormorbid conditions treated with intracranial radiosurgery. Between January 2004 and April 2009, 6 patients with multiple sclerosis and 14 patients with a collagen vascular disease were treated with gamma knife radiosurgery (GKRS) for intracranial tumors. Treated lesions included 15 total brain metastases in 7 patients, 11 benign brain tumors, one low grade glioma, and one cavernous malformation. Electronic records were evaluated for each patient to assess for toxicity. Toxicities were graded by the SOMA/LENT scale. In addition, “rare toxicities” were characterized as those reported in the scientific literature at an incidence of less than 5% after GKRS. Median follow-up time was 16 months. Median dose to the tumor margin was 13.0 Gy (range, 12 to 21 Gy) to the 50% isodose line. Median size of tumor treated with radiosurgery was 5.0 cc (range, 0.14 to 7.8 cc). Of the 14 patients with collagen vascular disease, none experienced a grade 3 or 4 toxicity or a toxicity characterized as rare. Of the 6 patients with multiple sclerosis, 3 patients experienced rare toxicities, and two of these were grade III toxicities. Rare complications included a patient experiencing obstructive hydrocephalus, as well as two patients with motor cranial nerve palsy. High grade toxicities included the patient with an acoustic neuroma requiring VP shunt placement for obstructive hydrocephalus, and one patient with a vestibular schwannoma who experienced facial nerve palsy and who was offered tarssoraphy for a non-closing eye. Time interval between radiosurgery and high grade toxicities ranged from 1 week to 4 months. While our series is limited by small numbers, it suggests that patients with multiple sclerosis who receive GKRS may be at increased risk of rare and high grade treatment-related toxicity. Given the time course of toxicity, treatment-related edema or demyelination represent potential mechanisms.