Predictive Factors of Biological Behaviour in Pituitary Adenoma

Background: Predicting biological behavior of pituitary adenomas is a complex but highly desirable issue for both scientific and practical porpoises. Recently, a clinico-pathological grading based on histopathological and neuroradiological features has been proposed, stratifying the risk of progression/recurrence in 5 classes. Aim of our study is to perform an independent external validation of this score and identify other potential predictor of aggressive behaviour. 
Results: Five hundred sixty-six patients with pituitary adenomas were included in this study (253 FSH/LH, 147 GH, 85 PRL, 72 ACTH and 9 TSH tumors). In 437 cases, pituitary adenomas were non-invasive, with low (grade 1a: 378 cases) or high (grade 1b: 59 cases) proliferative activity. In 129 cases, tumors were invasive, with low (grade 2a: 87 cases) or high (grade 2b: 42 cases) proliferative activity. During the follow-up (mean: 5.8 years), 60 patients developed disease recurrence or progression, with a total of 130 patients with pituitary disease at last follow-up. Univariate analysis demonstrated a significantly higher risk of disease persistence and recurrence/progression in patients with PRL, ACTH and FSH/LH tumors as compared to those with somatotroph tumors, and in those with high proliferative activity (grade 1b and 2b) or >1 cm diameter. Multivariate analysis confirmed that tumor type and grade are independent predictors of disease free-survival and progression free-survival. Tumor grading resulted the first parameter emerging in the decision tree analyses with CHAID growing process to stratify patients according to the risk of recurrence/progression. Conclusions: Our data confirmed the validity of Trouillas’ score, being tumor type and grade independent predictors of disease evolution. Therefore, we recommend to always consider both features, together with tumor histological subtype, in the clinical setting to early identify patients at higher risk of an aggressive behaviour.