The surgeon must decide what it is he or she wishes to achieve by operating and make this aim clear to the patient. Surgery usually has one of four aims that sometimes overlap:
• Total tumor removal to produce an endocrine cure.
• Debulking of a large multilobular tumor before radiotherapy.
• Decompression of the chiasm and optic nerves to either treat existing visual failure or prevent further encroachment of tumor that lies adjacent to the optic apparatus.
• Biopsy alone, which may sometimes be required without debulking when the radiologic diagnosis is unclear and further therapy undecided. An example of this is an operation to differentiate between sellar neurosarcoid and tuberculosis.
For microadenomas with hormone overproduction, the goal is early and permanent control of elevated hormone levels. This can only be achieved with total surgical removal. Subtotal removal of tumor in such cases may achieve temporary improvement in symptoms, but recurrence is inevitable unless some other adjuvant therapy is used, such as radiotherapy or medical therapy. Such a compromise delays control of elevated hormone levels and increases the inconvenience to the patient and also the cost of treatment. Therefore, there is often a good case for re-exploration if a microadenoma is not cured at the first operation, provided the endocrine diagnosis is certain. This is especially worthwhile where pathologic evidence of an adenoma is confirmed at the first operation.
For macroadenomas, complete resection is also the aim, but in practice, the ability to achieve complete removal of large tumors may be limited by lateral extensions or true pathologic invasion of the cavernous sinus or the dura.
Debulking of a large macroadenoma with visual symptoms may achieve considerable improvement in vision even without a complete resection. Headache may also improve with debulking, although curiously, headache related to small growth hormone (GH) secreting tumors may persist if the acromegaly is not cured, even when there is no residual tumor seen on scanning.
Tumors discovered as incidental radiologic findings require hormonal and visual assessment to assess the potential benefits of surgical treatment. Radiologic signs that are atypical for an adenoma suggest that surgery should be carried out to obtain a diagnosis. A subclinical field defect may be discovered, which warrants surgery to prevent progression. Evidence of subclinical hypopituitar-ism may be an added indication for surgery, as tumor removal can result in restoration of normal pituitary function. This contrasts with the commonly held and voiced view of endocrinologists in the 1980s and 1990s that surgery results in loss of function. Where these investigations are normal, surgery should be considered if the tumor is closely juxtaposed to the chiasm, to remove the risk of visual deterioration, or if serial magnetic resonance imaging (MRI) demonstrates progression.
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