The majority of pituitary tumors are histologically benign. However, local dural invasion is not uncommon (31). Occasionally such tumors are more aggressive, and rarely, central nervous system (CNS) or more distant metastases are present, indicating pituitary carcinoma in 0.2% of all primary pituitary tumors (32). Such malignant tumors are frequently functional, and treatment of the primary is directed toward local excision, radiotherapy, and, where appropriate, medical therapy such as dopamine agonists or octreotide.
Recurrent disease after previous radiotherapy presents a difficult management problem with progressive visual loss and neurologic disability proceeding to rapid death in many cases. Careful surveillance with neuroimaging and hormonal assessment is required, particularly to facilitate planning of further intervention and to assess responses to treatment. Commonly, standard three-field external beam irradiation has been delivered, making further treatment of this type limited because of toxicity to the optic chiasm. "Salvage" stereotactic radiotherapy with the Gamma Knife or sterotactic multi-arc radiotherapy (SMART) may be considered in individual patients. Although no controlled trials have been performed, cytotoxic chemotherapy has also been used in select cases. The response rate is variable, and progressive disease has been observed in most reports (33). Targeted radioisotope treatment, such as 90Y-labelled somatostatin analogs, may have a role in this rare condition in the future.
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