MRI T2-Weighted Signal Characteristics of Nonfunctioning Pituitary Adenomas Do Not Predict Extent of Tumor Resection from Transsphenoidal Surgery: Results of a Prospective Multicenter Surgical Study

Introduction: Others have demonstrated that MRI T2-weighted pituitary adenoma signal characteristics may predict tumor firmness, and, consequently the difficulty of tumor removal. It is not known if tumor T2 signal can predict extent of tumor resection, however. If such a relationship existed, it would be helpful prognostic information for surgeons. In this study, we investigated the relationship between the T2-weighted adenoma signal and extent of surgical resection in a multicenter prospective study of patients with surgically treated nonfunctioning adenomas.

Methods: Data from a prospective multicenter study including seven United States centers and 15 surgeons was analyzed. The T2-weighted signal of the adenoma was classified as hypointense, isointense, or hyperintense by comparison with the normal pituitary tissue or normal temporal lobe gray matter on coronal T2-weighted sequences as described by Potorac et al[1] MRI scans were centrally adjudicated by reviewers blinded to patient outcome. Extent of tumor resection was dichotomized as gross-total resection (GTR) versus subtotal resection (STR). Tumor volumes were determined using semiautomated segmentation (3D Slicer). Patient and tumor characteristics were also compiled and analyzed using standard statistical techniques.

Results: A total of 219 patients with satisfactory preoperative MRI scans and extent of tumor resection data comprised the study cohort. The adenomas were hyperintense in 109 cases (49.8%), hypointense in 11 cases (5.0%), and isointense in 99 cases (45.2%). For hyperintense tumors, gross-total resection was achieved in 86 patients (78.9%). Mean percent resection was 98.1% ± 5.5. For hypointense tumors, GTR was achieved in 8 patients (72.7%), with mean percent resection 96.9% ± 6.2. For isointense tumors, GTR was achieved in 84 (84.8%), with mean percent resection 97.6% ± 7.7. There was no significant difference in extent of resection among the 3 groups in either GTR achieved or percent tumor removal (p = 0.73). Logistic regression analysis demonstrated that other tumor characteristics, such as maximum tumor diameter >40 mm (p = 0.027, OR: 7.197, 95% CI: 1.26–41.2), tumor extension into the frontal/temporal lobe, posterior fossa, or ventricle (p = 0.042, OR: 3.759, 95% CI: 1.05–13.5), and Knosp Grade 3–4 (p = 0.001, OR: 4.581, 95% CI: 1.94–10.8) were independent predictors of subtotal resection.

Conclusion: In this multicenter prospective study, the T2-weighted signal of pituitary adenoma did not predict extent of tumor resection in patients with nonfunctioning pituitary adenomas following transsphenoidal surgery. Mean percent tumor removal was greater than 96% in hypointense, isointense, and hyperintense tumors.

• Reference

• 1 Potorac I, Petrossians P, Daly AF. , et al. Pituitary MRI characteristics in 297 acromegaly patients based on T2-weighted sequences. Endocr Relat Cancer 2015; 22 (02) 169-177