Treatment This varies with the type and size of the pituitary tumor, the status of the endocrine and visual systems, and the age and childbearing plans of the patient. The administration of the dopamine agonist bromocriptine (which inhibits prolactin) in a beginning dosage of 0.5 to 1.25 mg daily (taken with food) may be the only therapy needed for small or even large prolactinomas, and is a useful adjunct in the treatment of the amenorrhea–galactorrhea syndrome. The dose should be slowly increased by 2.5 mg or less every several days until a therapeutic response is obtained. Under the influence of bromocriptine, the tumor decreases in size within days, the prolactin level falls, and the visual field defect improves.
Some cases of acromegaly also respond to the administration of bromocriptine but even better to octreotide, an analogue of somatostatin. The initial dose of octreotide is 200 mg/d, increased in divided doses to 1,600 mg by increments of 200 mg weekly. In Lamberts’ series of acromegaly patients, the growth hormone levels returned to normal and tumor size was reduced in 12 of 15 cases. Treatment with bromocriptine and octreotide must be continuous to prevent relapse. Newer slow-release somatostatin analogues and long-acting dopamine agonists such as cabergoline have been developed for use in patients who do not respond to the conventional agents (Colao and Lombardi).
If the patient is intolerant of medication (or, in the case of acromegaly, to octreotide and newer drugs), the treatment is surgical, using a transsphenoidal microsurgical approach, with an attempt at total removal of the tumor and preservation of normal pituitary function. Unfortunately, approximately 15 percent of GH-secreting tumors and prolactinomas will recur at 1 year. For this reason, incomplete removal or recurrence of the tumor (or tumors that are unresponsive to hormonal therapy) should be followed by radiation therapy.
Alternative primary treatment for intrasellar tumors is forms of stereotactic radiosurgery, provided that vision is not being threatened and there is no other urgent need for surgery. These forms of radiation can be focused precisely on the tumor and will destroy it. Kjellberg and
Kliman in past decades using proton beam radiation, in the past treated more than 1,100 pituitary adenomas without a fatality and with few complications (Kliman et al).
A single brief exposure was all that was necessary. An endocrine deficit will follow in most instances and must be corrected by hormone replacement therapy. Several equivalent methods (Gamma Knife, Cyberknife) are more accessible and have become widely used. The advantage of these radiotherapeutic methods is that tumor recurrence is rare. A disadvantage is that the radiation effect is obtained only after several months. Estrada and colleagues have also reported that external beam-radiation therapy may be employed after unsuccessful transsphenoidal surgery for Cushing disease. After approximately 3.5 years following radiation, 83 percent of their patients showed no signs of tumor growth. There are a few reports, however, of a decline in memory ability after radiation treatment of all types.
Large extrasellar extensions of a pituitary growth must be removed by craniotomy, usually with a transfrontal approach, followed by radiation therapy. Visual field defects often remain, but some improvement in vision can be anticipated.