Incidence of intracranial radiation necrosis following postoperative radiation therapy for sinonasal malignancies.

OBJECTIVES/HYPOTHESIS Surgery and postoperative radiation therapy are commonly used in the treatment of advanced sinonasal cancer. However, post-treatment radiation changes to the brain often mimic radiologic findings suggestive of tumor recurrence, leading to potential unnecessary intracranial biopsies. The objective of this study was to determine clinical factors that predict signs of tumor recurrence versus radiation necrosis in post-therapy sinonasal malignancies with intracranial extension. STUDY DESIGN Retrospective study. METHODS Twenty-six patients with sinonasal malignancy with intracranial extension underwent surgery and radiation ± chemotherapy between 2010 and 2014 at the University of Arizona. We analyzed sinonasal cancer type, stage, total radiation dosimetry, time until imaging changes, surgical pathology, associated imaging, and patient demographics. RESULTS Thirteen of 26 patients had postoperative imaging changes seen on surveillance magnetic resonance imaging (MRI). Five were deemed to have tumor recurrence due to new metastasis seen on positron emission tomography/computed tomography scan. Four patients were observed with serial imaging that confirmed pseudoprogression. In four patients, there was sufficient concern due to persistent MRI changes, which prompted surgical biopsy, and only one of them was positive for tumor recurrence. Factors that favored tumor recurrence included faster onset of imaging changes on MRI (55 vs. 186 days, P < .05). CONCLUSIONS Intracranial tumor recurrence can be difficult to distinguish between radiation necrosis in sinonasal cancers treated with surgery and postoperative radiation ± chemotherapy. Patients with sub-total resection and rapid onset of MRI changes in postsurveillance scans are more likely to have tumor recurrence versus radiation necrosis. Future imaging techniques or tests that investigate tumor biomarkers are necessary to prevent unnecessary biopsies. LEVEL OF EVIDENCE 4 Laryngoscope, 126:2445-2450, 2016.