Natural history of post-operative non-functioning pituitary adenomas - a single centre cohort analysis

To study behaviour of endonasally operated non-functioning pituitary adenomas (NFPA) and propose a cost-effective stratified follow-up regimen.

A single centre retrospective cohort analysis from June 2009 till December 2019. All endonasally operated pituitary adenomas were identified with sub-analysis of the NFPA's. Patients of all age groups with radiological follow-up more than 30 months were included. Patients with any kind of cranial intervention performed < within 30 months of surgery were excluded. The post-operative MRI for this cohort was evaluated until either any intervention was performed or until the last follow-up. The maximal tumour diameter in any plane (mm) was measured from the MRI scans. The annual growth rate and the statistical relationship between age, sex, IHC, Ki-67, resection %, residual tumour was calculated.

Out of 610 pituitary adenomas identified in the dataset, 116 patients met the inclusion criteria. Follow-up period ranged from 30 to 142 months (mean 78.5 months). A strong relationship existed between predicting tumour progression with first post-operative residue size (p = .001). A statistically significant relationship was found to be present between tumour growth and a residue of less than 10 mm diameter and 11-20 mm in diameter (Log rank p value .0216). On average, each patient with a residue < 5mm had MRI scans costing 976 £.

Based on statistical analysis and internal validation of the growth rate of the residue, we have proposed MRI follow-up scans. These recommendations have the potential to save more than 300 £per patient towards MRI costs and can lay down a marker for defining time interval of serial scans for post-operative NFPA's.