Transnasal-transsphenoidal yttrium-90 pituitary implantation in the therapy of acromegaly.

Abstract

Pituitary implantation of yttrium 90 is only one of many forms of therapy for acromegaly, an endocrine disorder resulting from an increased production of the growth hormone of the gland. Rasmussen et al. first suggested in 1953 (1) the use of Y90 for pituitary destruction, and in 1955 published with Yuhl and other co-workers (2) the clinical results in cancer patients. In 1959 Dogliotti, Ruffo, and Molinatti (3) described their experiences with multiple free pellets of Y90 implanted by the transsphenoidal route into the pituitary gland for the therapy of acromegaly, and in 1962 Molinatti et al. (4) reported 16 cases treated in this fashion. These last-named authors stated the difficulties of obtaining an even distribution of irradiation in the gland. The amount of Y90 employed ranged from 14.8 to 42 mCi with as many as five pellets being used in some cases. Joplin, Fraser, et al. (5) in 1961 reported their results with needle implantation of radioactive gold, AU198, in the therapy of acromegaly and with Y90 in the retreatment of 4 cases. In 1965, Hartog and his associates (6), supplementing Joplin's original report, gave results in these cases and the overall outcome of treatment with free pellets of AU198, Y90, or both isotopes in 22 acromegalic patients. Forrest et al. in 1958 (7) introduced the screw technic. With this method, Y90 is encased in a nylon jacket and attached to a stainless-steel screw with a threaded base which is screwed into the anterior wall of the pituitary fossa. The procedure has two noteworthy features: maintaining the intrasellar Y90 source and sealing the entry site to avoid cerebrospinal fluid rhinorrhea. Maintaining the fixed position of the sources is admirably accomplished, whereas the avoidance of rhinorrhea remains to be proved (8). Forrest, as early as 1956, used multiple rods of Y90 implanted by the transnasal route for the therapy of acromegaly (9), but after treating 8 patients he switched to AU198. The purpose of this paper is to present our experiences in the therapy of acromegaly with multiple sources of Y90 introduced into the sella turcica by means of the transnasal, transsphenoidal route and the utilization of the screw implant technic of Forrest (7) to achieve and maintain proper distribution of the sources. Method Nine patients who were considered to have active acromegaly, although without signs of optic nerve compression or evidence of suprasellar extension, were treated. Y90 rods were implanted in the enlarged pituitary according to the screw-implant technic of Forrest. Activity was determined by serum growth hormone measurements, chemical tests measuring indirectly increased growth hormone, and clinical signs and symptoms. Dosimetry and Implant Planning The radioactive isotope, yttrium 90, has a half-life of sixty-four and twotenths hours and decays by beta particle emission to stable zirconium 90.