Pituitary Irradiation for Acromegaly

Abstract

Although irradiation for the treatment of acromegaly was introduced more than fifty years ago (1, 4), there is still lack of complete agreement on the selection of responsive cases and on optimal technic. Irradiation was first used for pituitary adenomas because of the high mortality and morbidity associated with surgical procedures on the hypophysis. Subsequently, its value was proved and it remains the procedure of choice except in patients with large tumors of long standing or with visual field defects sufficiently critical to require immediate decompression (2). In the latter group radiation is generally administered only after partial hypophysectomy for decompression. At present, external gamma or roentgen rays are commonly used, but surface applications or implants of radium (5), radioyttrium (8), colloidal chromic phosphate (10), and even the collimated proton beam from the synchrotron (7) have been employed. Over the years, two technics of radiation therapy for pituitary adenoma have evolved. The first was the “interval” technic, in which a pituitary dose varying from a few hundred to one or two thousand roentgens was given, and, after a period of observation of several weeks or months, the course of therapy was repeated if necessary. This approach was based on (a) the observation that certain patients do not require a larger dose, and (b) the concept that overfunction probably occurs cyclically and is logically treated by cyclic therapy. The alternate or “single-course” technic recognizes the uncertainty in dose necessary to control acromegaly in a particular patient and assumes that the disease will be more readily controlled by administration of an initial dose as high as is consistent with safety to the peripituitary structures (6). In addition to the loss of time entailed by the multipledose technic, the total dose with several courses of therapy frequently exceeds that of the larger single course and may, in the end, result in greater damage to surrounding normal structures. The available published data, summarized by Buschke (2), suggest that the single intense course produces the more satisfactory results. This paper presents the experiences gained between January 1942 and March 1959 at the University of California Hospitals, San Francisco, with radiation therapy for acromegaly in 37 patients. During this time the diagnosis of acromegaly was made in a total of 65 patients. Seven cases were discarded because of inadequate information. Of the remaining 58, 9 were considered quiescent and required only supportive or symptomatic treatment; 2 patients had hypophysectomy for marked visual impairment and 1 was treated by estrogen therapy alone.