Endocrine Remission After Pituitary Stereotactic Radiosurgery: Differences in Rates of Response for Matched Cohorts of Cushing Disease and Acromegaly Patients

Abstract

To compare and describe the time to endocrine remission and new hypopituitarism among patients with growth hormone (GH) and adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas after radiosurgery, controlling for several known prognostic factors. An institutional review board-approved, institutional retrospective analysis of patients with GH- and ACTH-secreting pituitary adenomas was performed, with matching for patient sex, age at radiosurgery, interval between the last resection and radiosurgery, use of previous radiation therapy, whole sella treatment, suprasellar extension, cavernous sinus invasion, and margin dose. Endocrine remission was defined as a normal serum insulin-like growth factor-1 (GH secreting) or a normal 24-hour urine-free cortisol (ACTH secreting) level without suppressive medications. Endocrine remission and the incidence of new hypopituitarism after single-fraction radiosurgery were recorded and compared between the 2 groups. The data from 242 patients were evaluated, 121 with GH-secreting tumors and 121 with ACTH-secreting tumors. Of the 242 patients, 75% had cavernous sinus invasion and 10% had suprasellar extension at radiosurgery. The median radiosurgical marginal dose was 25Gy to the 50% isodose line between each group. After multivariable adjustment, the factors associated with an increased time to endocrine remission included patient age (hazard ratio [HR] 1.016; P=.023), cavernous sinus invasion (HR 1.793; P=.004), and the presence of acromegaly (HR 2.912; P<.001). The incidence of new hypopituitarism developing after stereotactic radiosurgery was 29% and did not appreciably differ by adenoma subtype (P=.180). After radiosurgery, patients with ACTH-secreting tumors achieved endocrine remission sooner than did those with GH-secreting tumors. These results provide insight into the relative tumor biology and disease course after radiosurgery that will serve to further improve clinical outcomes and patient treatment in the future.