Predicting extent of resection in transsphenoidal surgery for pituitary adenoma

Abstract

Background: The extent of resection (EOR) is a crucial outcome parameter in transsphenoidal pituitary surgery (TSS), and is linked to endocrinological outcome, postoperative morbidity, and mortality. We aimed to build a robust, quantitative, and easily reproducible imaging score able to predict EOR in TSS. Methods: The ratio (R) between the maximum horizontal adenoma diameter and intercarotid distance at the horizontal C4 segment was used to stratify our patient series in four classes: class I R ≤ 0.75, class II 0.75 < R ≤ 1.25, and class III R ≥ 1.25. Class IV included adenomas which completely encased the internal carotid artery. The resulting score was internally validated for robustness. Results: One hundred sixteen patients were included in the study, of which 96 (83%) for derivation and 20 (17%) for validation. EOR showed significant differences between grades (grade I, 100%; II, 97.9%; III, 94.2%; IV, 87.2%; all P < 0.05). The same applied to residual volume (RV) (grade I, 0 cm3; II, 0.08 cm3; III, 1.11 cm3; IV, 1.63 cm3; all P < 0.05). Differences in gross total resection (GTR) were statistically significant among classes I, II, and III (P < 0.05). The incidence of residual adenoma in the cavernous sinus increased also constantly from grade I up to grade IV although a significant difference was only found between grades III and II (P = 0.004). The score performed equally well in the validation cohort. Inter-observer agreement was high, with intraclass correlation coefficients > 0.89 for measurement of both the horizontal tumor diameter and the ICD among two independent raters (P < 0.001). Conclusions: The proposed score is a simple and reproducible tool which reliably predicts surgical outcome including EOR, RV, and GTR of pituitary adenoma patients undergoing TSS.