Application of radiosurgery in the treatment of pituitaryadenoma

Overview

adenomaThe goal of pituitary adenoma radiosurgery is to halt tumor growth, to normalize hormonalhypersecretion if present, and to maintain the performance of a normal hypophysis andfunctionally important structures around the sella, namely the optic nerve. The minimumdistance required between the irradiated target and the optic pathway should be reassessed.For Gamma knife model B (or C) the limit should be 2 mm for secreting adenomas and, in thecase of non-secreting adenomas, direct contact of the adenoma with the optic chiasm may betolerated where only a short segment is affected of the visual pathway. During the midterm ofthe follow up period, an anti-proliferative effect was achieved in all 305 evaluated patients and70% of adenomas decreased in size usually within 2 years following radiosurgery. Hormonalnormalisation of hypersecreting adenomas is comparable with the results of transsphenodialmicrosurgery, apart from the latency, which is usually 2 years.During this period hypersecretionwas arrested in 38 % of patients with acromegaly, in 90% with Cushing’s disease and in 54%with prolactinoma. The most important factor influencing post-irradiation hypopituitarismseems to be the mean dose applied to the hypophysis. The current position of radiosurgery inthe majority of cases is as an adjuvant treatment for residual or recurrent adenomas afterprevious microsurgery. In selected cases radiosurgery may be used as a primary treatment, e.g.in patients with contraindications of overall anaesthesia in patients, where the treatment effectis not urgent in the patients who refuse to undergo open surgery.

Key words:
pituitary adenoma - radiosurgery - gamma knife.