THE MANAGEMENT OF HISTOLOGICALLY UNVERIFIED PRESUMED CEREBRAL GLIOMASWITH RADIOTHERAPY

Purpose: To define the natural history, and prognostic factors of pati ents with histologically unverified presumed gliomas diagnosed on CT o r MR imaging, and treated with external beam radiotherapy. Methods and Materials: Retrospective review of 111 adults with histologically unv erified presumed cerebral glioma treated with radiotherapy between 197 4 and 1990. Using CT or MRI criteria alone 41 were presumed low grade, 63 high grade gliomas and 7 were unclassified. Survival results were compared to a cohort of 82 adults with histologically verified low gra de gliomas treated over the same period with surgery and radiotherapy. Results: The 5 year survival probability of the whole cohort was 31%. Age, performance status, and the degree of contrast enhancement were independent prognostic factors for survival. Patients with presumed lo w grade glioma had a 5 year survival of 41% compared to 52% for patien ts with verified low grade glioma. After correction for prognostic fac tors no significant difference was found in the survival between patie nts with verified and unverified low grade tumors. One of 15 cases wit h subsequent histology, obtained at autopsy or salvage surgery, had no nglial pathology. Conclusion: Patients diagnosed on the basis of clini cal features and imaging as having presumed glioma have similar natura l history and clinical behavior after treatment with radiotherapy to t hose with histologically confirmed gliomas. However, the results shoul d not be taken as justification for avoiding biopsy. A proportion of p atients may have nonglial pathology and new more effective treatment s trategies for patients with glial tumors can only evolve on the basis of full diagnostic information including pathology.