Predicting early post-operative remission in pituitary adenomas: evaluation of the modified knosp classification

Cavernous sinus invasion by pituitary adenomas is an important prognostic factor for evaluating the possibilities of complete remission and to guide patient management. A widely used Magnetic Resonance Imaging grading system, suggested by Knosp in 1993, has recently been revised by the same group. The aims of our study were to apply this revised grading system to our surgical series, to determine its association with surgical outcomes, gross-total resection (GTR) and endocrinological remission (ER), paying particular attention to grades 3A and 3B, which represent the novelty of this revised classification.

We included consecutive patients who underwent endoscopic endonasal surgery for a macroadenoma from September 2012 to December 2016. MRI images were reviewed and classified according to the revised Knosp classification. Surgical reports indicated the intra-operative CS invasion. GTR and ER were evaluated on 3-months post-operative MRI and endocrine evaluation.

254 patients were included in this study. We found a total rate of cavernous sinus invasion of 18.4%. Different outcomes were observed for each grade, with an increased rate of cavernous sinus invasion with each grade. Per-operative rates of invasion were 61.5 and 78.6% in grades 3A and 3B respectively. GTR was negatively correlated with the grade, while rates were 55.8% and 30.0% for grades 3A and 3B respectively.

The revised Knosp radiological classification contributes to the prediction of surgical outcomes and early ER in pituitary adenomas. To manage, as precisely as possible, the risk of early recurrence in pituitary adenomas, clinicians should also consider other recognized prognostic factors, such as the proliferative status of the tumor.