Impact of the extent of tumor resection on adrenal function recovery after transsphenoidal surgery for nonfunctioning pituitary adenomas

OBJECTIVE: While endonasal transsphenoidal surgery (ETS) is the standard treatment for nonfunctioning pituitary adenomas (NFPAs), the postoperative recovery rates of secondary adrenal insufficiency and their predictive factors remain poorly understood. The authors investigated the relationship between the tumor resection rate and adrenal function recovery in patients with NFPAs. METHODS: This retrospective study included 450 patients with NFPAs who underwent ETS between January 2013 and November 2023. The rates of preoperative hypopituitarism and postoperative recovery rates of secondary adrenal insufficiency and their associated factors were analyzed. Recovery was defined as normalization of serum cortisol levels without replacement therapy for at least 24 hours, accompanied by symptom resolution. The tumor resection rate was calculated as the percentage of the tumor volume resected. RESULTS: The median follow-up period for the entire cohort was 52 months (range 1-131 months). A total of 246 (55%) patients had dysfunction in one or more pituitary axes. Fifty-three (47%) of 114 patients with preoperative adrenal insufficiency showed postoperative adrenal insufficiency recovery. The cumulative adrenal insufficiency recovery rates were 12% at 1 month, 19% at 3 months, 32% at 6 months, and 41% at 12 months. Among the 114 patients with preoperative adrenal insufficiency, the factors associated with postoperative adrenal insufficiency recovery were investigated. Patients with smaller tumor sizes of < 20 mm (log-rank test, p = 0.001) and those with tumor resection rates of more than 85% (log-rank test, p = 0.032) demonstrated better postoperative adrenal insufficiency improvement. Bivariate Cox proportional hazards analysis demonstrated that smaller tumor sizes (continuous, HR 0.97, 95% CI 0.93-0.98; p = 0.043) and higher tumor resection rates (HR 1.03, 95% CI 1.01-1.07; p = 0.001) were significantly associated with better postoperative adrenal insufficiency recovery. Multivariable analysis confirmed that only higher tumor resection rates were significantly associated with better postoperative adrenal insufficiency recovery (HR 1.03, 95% CI 1.01-1.06; p = 0.019). CONCLUSIONS: Nearly half of the patients with preoperative adrenal insufficiency achieved recovery after ETS for NFPAs. The enhanced extent of tumor removal was an independent factor associated with better postoperative recovery, indicating that optimizing safe maximal resection procedures may be crucial in enhancing adrenal function.