Radiotherapy is usually delivered to the pituitary adenoma using daily frac-tionation (5 d/wk) to a dose of 45 Gy in 25-30 fractions. Higher doses of irradiation are no more effective in either of tumor control or survival because they carry higher morbidity. To avoid radiation toxicity, particularly to the optic chiasm and nerves, it is important to maintain a daily radiation dose of less than 2 Gy per fraction. Some centers have employed unconventional fractionations usually given in less than 5 wk to a lower dose assumed to be biologically equivalent to conventional daily irradiation. The long-term efficacy and toxicity of this approach compared with conventional radiotherapy is less well defined.
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