Temporal bone paraganglioma has been proved to be radioin-curable.27'40 Rapid tumor progression after radiation has been well documented.41-44 Failure rates vary from 15% to 30%.41-44 At the Univerisity of Zurich, 30% of the patients operated on presented with tumor progression in spite of planned curative preoperative irradiation with 5000 to 7000 R.22

The biologic response of this benign tumor to radiotherapy differs from that of malignant neoplasms. The effectiveness of irradiation is limited by the low mitotic rate of chief cells. Chief cells have been shown to persist for years after therapeutic doses of irradiation.7'38 Histologic analysis of surgical specimens of irradiated glomus tumors following surgical salvage has demonstrated formations of intact islands of vital chief cells.27 For all these reasons, radiation is indicated for the progression of unresectable lesions or progressing residual tumor.

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