Endocrine Remission after Pituitary Stereotactic Radiosurgery: Differences in Rates of Response for Matched Cohorts of Cushing’s 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 after 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 based on patient gender, age at radiosurgery, time interval between the last resection and radiosurgery, use of previous radiotherapy, whole sella treatment, suprasellar extension, cavernous sinus invasion, and margin dose. Endocrine remission was defined, off of suppressive medications, as a normal serum IGF-1 (GH-secreting) or a normal 24-hour urine free-cortisol (ACTH-secreting). Endocrine remission and the incidence of new hypopituitarism after single fraction radiosurgery were described and compared between groups. Two-hundred and forty-two (242) patients were evaluated, 121 with GH-secreting tumors and 121 with ACTH-secreting tumors. A total of 75% of patients had cavernous sinus invasion and 10% had suprasellar extension at the time of radiosurgery. The median radiosurgical marginal dose was 25 Gy to the 50% isodose line between each group. After multivariable adjustment, factors associated with increased time to endocrine remission included patient age (HR 1.016, p = 0.023), cavernous sinus invasion (HR 1.793, p = 0.004), and patients with acromegaly (HR 2.912, p < 0.001). The incidence of a new hypopituitarism developing after SRS was 29% and did not appreciably differ by adenoma subtype (p = 0.180). After radiosurgery, patients with ACTH-secreting tumors achieve endocrine remission sooner than those with GH-secreting tumors. These results provide insight into the relative tumor biology and post-radiosurgical disease course that will serve to further improve clinical outcomes and patient management in the future.