Predicting extent of resection in transsphenoidal surgery for pituitary adenoma

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. 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. 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 cm(3); II, 0.08 cm(3); III, 1.11 cm(3); IV, 1.63 cm(3); 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). 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.