A study of vestibular schwannomas using positron emission tomography and monoclonal antibody Ki-67

Objective: This study aimed to evaluate the role of positron emission tomog raphy (PET) as an in vivo determinant of tumor aggressiveness and growth. Study Design: The study design was a prospective pilot study. Setting: Positron emission tomography was performed at the Clarke institute of Psychiatry. AU patients were treated at the Sunnybrook Health Science C entre, Both institutions are affiliated with the University of Toronto, Tor onto, Canada. Patients: The study consisted of five consecutive patients with vestibular schwannomas with tumor size of I cm or larger within the cerebellopontine a ngle. One was a recurrent tumor and four were primary tumors. interventions: Preoperative PET studies were conducted using 18-fluorodeoxy glucose (FDG) as a radionuclide tracer to measure glucose metabolism within tumors. Tumors were processed and immunostained against Ki-67 nuclear anti gen; their proliferative potentials were quantified based on immunoreactivi ty of tumor cells, Main Outcome Measures: Tumor metabolic activity on PET was compared with th at of contralateral cerebellum to arrive at an FDG index. This number was c ompared with clinical parameters and Ki-67 reactivity. Results: On PET, all tumors showed less metabolic activity than the cerebel lum. The FDG uptake varied greatly between tumors independent of clinical p arameters. All the tumors had a low proliferative index (<5%) with immunohi stochemistry; there were quite a bit of intralesional variations in prolife rative activities. Conclusion: Large tumor size and recurrent disease did not correlate well w ith increased FDG uptake on PET. Similarly, they did not show increased cel lular activities as expressed by Ki-67 immunostaining.