Long-Term Surgical Outcomes Following Microscopic Transsphenoidal Surgery for Nonfunctioning Pituitary Neuroendocrine Tumors (NF-PitNETs): A 22-Year Single-Center, Single-Surgeon Cohort Study

Background/Objectives: Nonfunctioning pituitary neuroendocrine tumors (NF-PitNETs) frequently present with mass effect and may recur despite successful surgical treatment. Long-term outcomes from homogeneous surgical cohorts remain limited. Methods: We retrospectively reviewed consecutive patients who underwent microscopic transsphenoidal surgery (mTSS) of NF-PitNETs by a single surgeon at a tertiary center between 2003 and 2025. Demographic, radiographic, pathological, surgical, and follow-up data were analyzed. The primary outcome was recurrence, defined as loss of tumor control requiring additional treatment. Recurrence-free survival (RFS) was evaluated using Kaplan-Meier and Cox regression analyses. Results: A total of 381 patients were included with a median follow-up of 57 months. Median tumor size was 27 mm, and 98.5% were macroadenomas. Visual outcomes were available for 228 patients; 65.8% demonstrated postoperative improvement, while 4.8% worsened. Among 359 patients with available EOR data, GTR was achieved in 195 (54.3%), NTR in 89 (24.8%), and STR in 75 (20.9%). On multivariable logistic regression, Knosp grade >2 (OR 2.89, 95% CI 1.50-5.63; p=0.002) and subtotal resection (STR) (OR 7.62, 95% CI 3.25-17.83; p<0.001) were independently associated with recurrence. Cox regression demonstrated STR as the sole independent predictor of reduced RFS (HR 2.82, 95% CI 1.64-4.90; p<0.001). Conditioned RFS improved with longer recurrence-free intervals after GTR; however, late recurrences continued to occur, indicating persistent long-term risk. Conclusions: mTSS provides favorable visual outcomes and durable tumor control for most patients with NF-PitNETs. Knosp grade >2 and, particularly, STR are the strongest predictors of recurrence. Persistent late recurrence risk supports prolonged postoperative MRI surveillance.