The learning curve of endoscopic endonasal transsphenoidal surgery for pituitary adenomas with different surgical complexity

OBJECTIVE: To investigate the learning curve under different surgical complexity in endoscopic transsphenoidal approach for pituitary adenoma. METHODS: 273 patients undergoing endoscopic transsphenoidal surgery for pituitary adenoma were collected retrospectively and divided into three groups chronologically (early, middle, and late periods). Surgical complexity was differentiated based on Knosp classification (Knsop grade 0–2 vs. Knosp grade 3–4), tumor maximum diameter (MD) (macroadenomas vs. giant adenomas), and history of previous surgery for pituitary adenoma (first operation vs. reoperation). Then the temporal trends in operative time, surgical outcomes, and postoperative complications were evaluated from early to late. RESULTS: The median operative time decrease from 169 to 147 min across the three periods (P = 0.001). A significant decrease in operative time was seen in the simple groups [Knosp grade 0–2 adenoma (169 to 137 min, P < 0.001), macroadenoma (166 to 140 min, P < 0.001), and first operation (170.5 to 134 min, P < 0.001)] but not in their complex counterparts (P > 0.05). The GTR rate increased from 51.6% to 69.2% (P = 0.04). The surgical period was an independent factor for GTR in the simple groups [Knosp grade 0–2 adenoma: OR 2.076 (95%CI 1.118–3.858, P = 0.021); macroadenoma: OR = 2.090 (95%CI 1.287–3.393, P = 0.003); first operation: OR = 1.809 (95%CI 1.104–2.966, P = 0.019)] but not in the complex groups. The biochemical cure rate increased over periods without statistical significance (from 37.5% to 56.3%, P = 0.181). Although intraoperative CSF leakage rose (from 20.9% to 35.2%) and postoperative CSF leakage reduced (from 12.1% to 5.5%), there was no statistically significant trend across the three time periods (P > 0.05). CONCLUSION: This study showed that complex operations might have a prolonged learning curve. Differentiating surgical difficulty and using multivariate combined analysis may be more helpful in clinical practice.