For residual disease following surgery, the options include medical therapy or radiation therapy. Given the novel medical therapies available, growth hormone control should be achieved in most patients.
There are 3 medical therapies:
Somatostatin analogs are administered as intramuscular injections once a month. In the U.S., the analogs octreotide LAR (long-acting release) and lanreotide depot are available and control GH and IGF-1 levels in approximately 2/3 of patients. Octreotide and lanreotide lead to improvement in symptoms in the majority. In about 40% of patients, the tumor can shrink modestly as well. In selected patients, when the tumor is not completely removable and is not causing visual loss, somatostatin analogs may be used as initial therapy in lieu of surgery. Side effects include digestive problems such as loose stools, nausea, and gas in one third of patients. In addition, approximately 25 percent of patients develop gallstones, which are usually asymptomatic.
Dopamine agonists have been used largely as second-line medial therapy. Bromocriptine in divided doses of up to 20 mg daily reduces GH secretion from a small number of pituitary tumors. Side effects include gastrointestinal upset, nausea, vomiting, light-headedness when standing, and nasal congestion. Another dopamine agonist, cabergoline, may be more effective in controlling GH levels, in up to 39% of patients in one study. The dopamine agonists are oral preparations.
A growth hormone receptor antagonist, pegvisomant, is a novel approach to acromegaly treatment by blocking all peripheral effects of GH, resulting in decreased production of IGF-1, both locally and at the liver. Pegvisomant, administered as a daily subcutaneous injection, can be used in patients who do not respond to somatostatin analogs or other types of treatment or may be considered as first line therapy in selected patients. Pegvisomant is highly effective, and may normalize IGF-1 levels in up to 97% of patients. Potential complications include an increase in tumor size (uncommon) and changes in liver function tests. MRI scans and liver tests need to be monitored.
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Open trials refer to studies currently accepting participants. Closed trials are not currently enrolling, but may open in the future.