Transsphenoidal resection of the pituitary adenoma is the initial treatment of choice in patients with acromegaly. It is also the only treatment that is potentially curative. Because this patient's tumor is invading the left cavernous sinus and compressing the optic chiasm, complete resection will likely not be possible; however, surgery can effectively debulk the tumor and preserve vision in addition to significantly decreasing growth hormone (GH) secretion as measured by insulin-like growth factor 1 (IGF-1) levels. In patients in whom complete resection is not possible, such as this patient, additional therapy may be required such as stereotactic radiation therapy or medical therapy to inhibit GH secretion or block its effect on the tissues. However, surgical resection remains an essential first step in the treatment of acromegaly.

A small number of GH-secreting pituitary adenomas co-secrete prolactin. Although dopamine agonist therapy with agents such as bromocriptine would treat the associated prolactin elevation, it is minimally effective in acromegaly and would not adequately treat GH secretion or address the mass effect of a GH-secreting adenoma.

A GH receptor blocker, pegvisomant, is available. Pegvisomant works in the peripheral tissues as an antagonist to GH but does not decrease its production by the tumor. This patient needs intervention to treat mass effect at this time because the tumor is damaging the optic chiasm and the patient's vision, and this treatment would not be expected to decrease the tumor size.

Somatostatin analogues, such as octreotide and lanreotide, inhibit GH secretion and are helpful in treating some patients with acromegaly. They are used primarily in patients with unresectable tumors without significant mass effect or those with a contraindication to surgery. They may also be used in patients with continued GH secretion following incomplete transsphenoidal resection. However, they would not be an appropriate treatment in this patient with a large, invasive, vision-threatening pituitary tumor.

Radiation therapy may be added to surgical or medical therapy to help increase the chance for remission or cure. Radiation to the pituitary carries a high risk of causing pituitary insufficiency and damage to surrounding tissues (particularly the optic nerves); therefore, it is not usually an initial treatment for acromegaly in most patients. In those in whom it is used, stereotactic surgery (gamma knife) is the preferred approach to minimize potential complications.