Factors affecting early versus late remission in acromegaly following stereotactic radiosurgery

Stereotactic radiosurgery (SRS) is a well-established treatment modality for patients with acromegaly. Our previously published study demonstrated a median time to remission of 29 months. This study aims to identify factors affecting the timing of remission and also to quantify the rate of late remission. This is a retrospective analysis of acromegaly patients who underwent SRS between 1988 and 2016. Early and late remissions were defined based on our prior median remission time of 29 months. The median imaging and endocrine follow-ups are 66 and 104.8 months, respectively. Multivariate analysis was conducted to analyze factors leading to late remission. A total number of 157 patients, of those 102 (64.9%) patients achieved remission. of those 102 patients, 62 patients (60.7%) had remission in less than 29 months (early remission) whereas 40 patients (39.3%) achieved remission later than (late remission) 29 months. The two groups differed significantly in the time interval between the last resection and the first SRS (p = 0.040) whole sella radiosurgery (p = 0.025) or radiosurgery to the cavernous sinus (p = 0.041). Competing risk analysis showed the interval between resection and SRS was significantly longer in the late remission group (HR 1.013, 95% CI 1.004-1.02; p = 0.007). Fifty-one of 157 patients (32.5%) developed a new endocrine deficiency following SRS. Those with shorter time between resection and SRS were more likely to achieve early remission. While most patients achieve remission in less than 4 years, the latency of effect with SRS yields a small percentage of patients achieving remission beyond that time point.