Untreated acromegaly is associated with a very high morbidity. The aim of therapy is to achieve a mean growth hormone level of less than 5mU/L, which is the level that has been associated with a decrease in mortality. The treatment options that are available are surgery, pharmacalogical and radiotherapy.
The main two types of drugs available for the treatment of acromegaly are the dopamine agonists and the somatostatin analogues. Dopamine agonists alone can be given to patients to try to shrink tumours prior to surgery and also to control their symptoms. Dopamine agonists are probably most successful at treating mixed growth hormone and prolactin secreting tumours. The dopamine agonists that are used are bromocriptine (10-60mg/day) or cabergoline (0.5mg/day). When these drugs are used, they should be started slowly as they are associated with unpleasant side-effects such as nausea and vomiting. The dopamine agonists have been largely replaced by the somatostatin analogues in recent years.
Octreotide is a synthetic analogue of somatostatin and is now being used to suppress growth hormone levels. It is given by subcutaneous injections (50-200µg 8-hourly) but a long-acting preparation is now available. The somatostatin analogues are generally well tolerated but they have been associated with an increased incidence of gallstones.
Although these pharmacological interventions do seem to induce some tumour shrinkage, the treatment of choice for a tumour that is anatomically causing symptoms is surgery.
The first-line therapy for acromegaly is surgery. Trans-sphenoidal surgery is generally agreed to be the most appropriate therapy for small intrasellar tumours of less than 1cm in diameter. This type of surgery for microadenomas seems to achieve clinical remission in approximately 60% of patients. The details of this type of surgery are found in the surgery section.
As the size of the tumour increases the percentage of patients that achieve complete clinical remission decreases. In cases when there seems to be incomplete tumour removal, radiotherapy is usually considered.
Radiotherapy is normally used in post-surgical cases where growth hormone levels have failed to normalise. The radiotherapy treatment is often combined with drug treatment for more beneficial results. The radiotherapy is usually performed over a 4-6 week period using conventional external radiation (maximum dose 4500 rad (cGy)). The radiation is given through multiple fields to reduce the risk of damage to the parasellar structures.