Acromegaly

Transsphenoidal Surgery

The most commonly used procedure for removal of adenoma from the pituitary is transsphenoidal surgery.

• The Role of Surgery
• Effectiveness
• Transsphenoidal Surgery
• Biochemical Cure Rate After Surgery
• Options for Patients Whose Surgery Fails

The Role of Surgery

The goals of surgery, as with all acromegaly therapies, include normalizing GH and IGF-1, eliminating mass effect from the tumor, and alleviating associated morbidities (1). Additional goals of surgery include preserving normal pituitary function, preventing recurrence of the tumor, and obtaining tissue for analysis. Advantages of surgery include rapid lowering of GH and the possibility of cure. Limitations include lower success rates with larger invasive tumors and/or less experienced surgeons. The guidelines recommend that surgery be considered as the first therapeutic option in all patients with acromegaly. Patients with mass effects will require surgery on an urgent basis. For patients not eligible or unwilling to undergo surgery, medical therapy can be selected.

Effectiveness

Several factors need to be considered in the surgical management of acromegaly:

• Surgical resection of the adenoma when not contraindicated is the initial treatment for acromegaly. Contraindications include:
  • Patients who are poor surgical or anesthesia risks because of age or poor general health.
  • Patients who delay surgery because they want to maintain pituitary function, e.g., women who want to become pregnant.
  • Patients who refuse surgery.
• Cure rates reach 90% in patients with small, well-defined microadenomas (size < 10 mm), and surgery provides rapid symptomatic relief (2).
• Cure rates for patients with macroadenomas (size >10 mm), which comprise the majority of GH tumors, are only 48% (2).
• Relapse may occur with macroadenomas, particularly those with extrasellar growth, after an initial improvement or apparent cure because of incomplete removal of tumor tissue (3).

Risk of complications is related to tumor size and the type of surgical procedure used, the most common procedure being transsphenoidal surgery. Recent retrospective studies of the results of surgical treatment for acromegaly showed that the risk of postoperative complications was 5% to 8% (2,4).

Transsphenoidal Surgery

In this invasive procedure, a neurosurgeon enters through the nose and approaches the pituitary through the sphenoid bone at the base of the skull. Occasionally, large pituitary tumors may require transcranial surgery, in which the surgeon cuts into the skull (above the eye and ear) and retracts a portion of the brain to reach the tumor.

	A patient healing from a translabial transsphenoidal surgery. (The upper lip is retracted to show the incision.) Beckers A. Pituitary Adenomas. An Interactive Resource for Your Library. Basel: Novartis Pharma AG, 2001.
	The transnasal route is less invasive, but provides limited visibility and poorer control of hemostasis.

Biochemical Cure After Surgery

A retrospective study of 162 patients who underwent surgery for acromegaly between 1978 and 1996 used a stringent definition of biochemical cure: GH <2.5 ng/mL after OGTT and normalization of the IGF-1 level (2). The overall surgical cure rate was 57%, but was 91% for microadenomas and 48% for macroadenomas. Adjuvant radiation and/or pharmacologic therapy was given to 61 patients. The 10-year survival rate was 88%, and there was no difference in mortality between the patients in remission and a control sample.

Options for Patients Whose Surgery Fails

A second transsphenoidal surgery is rarely an option for patients whose first surgery fails. Only 15% of these patients achieve biochemical remission (5). In addition, the risks associated with repeat transsphenoidal surgery are significantly greater in repeat procedures than in first-time procedures (6).

When surgery fails to normalize GH levels, or when the patient is not a candidate for surgery, acromegalic patients have the following options, according to AACE guidelines (PDF 93KB):

• Somatostatin analogues such as Sandostatin LAR® Depot (octreotide acetate for injectable suspension)
• Growth hormone receptor antagonists such as pegvisomant
• Radiation therapy