gms | German Medical Science

Objective: Atrophy of non-functioning pituitary adenoma has been described e.g. after radiotherapy; however, even in the case of considerable remnants after surgery, spontaneous shrinkage and relieve of mass lesion symptoms may happen in some cases. The aim of this study is to assess tumor shrinkage after transsphenoidal surgery and to identify its predictors.

Method: A total of 140 patients with postoperative remnants of non-functioning pituitary adenomas treated at our clinic were included in this study. All patients were operated by transsphenoidal procedure with 1.5 Tesla intraoperative MRI (iMRI) guidance. The intraoperatively depicted non-resectable remnants were compared to the results of MRI scans 3 months and 1 year after surgery. Age, gender, pre- and intraoperative tumor dimensions, growth pattern, endocrinological, ophthalmological and histological characteristics and history of previous pituitary surgery were analyzed as possible predictors using Fisher's exact test, Mann-Whitney test and multivariate regression table analysis.

Results: On follow-up imaging 3 months after surgery, 70 (50%) patients showed tumor remnant shrinkage of 0.5±0.6 cm³ which was 89±20% of the residual volume depicted by iMRI. In 45 (64%) cases the remnants disappeared completely. Age, gender, and preoperative tumor volume did not significantly differ in the two groups. Cystic tumor growth (p=0.02), additional resection of tumor remnants guided by iMRI (p=0.04), smaller volume (p=0.04) and smaller cranio-caudal diameter (p=0.0014) of remnants were positive predictors for postoperative shrinking. The following negative predictors were identified: growth into the cavernous sinus (p=0.009); history of previous pituitary surgery (p=0.0006) and tumor recurrence (p=0.04); and preoperative panhypopituitarism (p=0.04). On multivariate regression analysis, smaller tumor remnants (p<0.0001) and no history of previous pituitary surgery (p=0.003) did positively correlate with the shrinking volume. There was no spontaneous change of tumor remnant volume between 3 months and 1 year postoperatively. During a mean follow-up of 4.5 years, one (2%) patient with postoperative tumor shrinkage had to be revised due to recurrence.

Conclusions: Spontaneous tumor volume reduction of non-functioning pituitary adenoma remnants may be seen within 3 months after surgery. Smaller tumor remnant volume and no history of previous pituitary surgery are predictors of shrinkage on multivariate analysis.