Introduction: Transsphenoidal surgery (TSS) is the first line treatment for non-functioning pituitary adenomas (NFPA) which are symptomatic or in close proximity to the optic nerves. Currently, long-term MRI imaging is the recommended approach to monitor for NFPA recurrence or regrowth due the absence of reliable predictive markers. The necessary length of follow-up is unclear, as is the possibility of interrupting radiological follow-up after a certain period with a satisfactory result post TSS.
Method: We conducted a retrospective unicentric study on patients with NFPA who underwent TSS at Lausanne University Hospital between 2000-2022. The primary endpoint was the therapeutic outcome at three years (3Y) post TSS. Patients were categorized into three groups based on findings on MRI scans : complete resection (CR), stable residual adenoma (SRA), progressive residual adenoma (PRA). Age, sex, tumor size (diameter and volume), invasion and extension (Knosp classification), hormonal and visual defects, histological subtype and proliferation indexes were the main co-variates studied in association to the outcome. The secondary outcome was the incidence of NFPA progression past the three year time-point with an initially satisfactory outcome (CR or SRA) at five years or at last available follow-up.
Results: Out of one hundred and fourteen potentially eligible cases, we included eighty-five patients. Main reasons for exclusion were absence of consent, incomplete data or unclear diagnosis. The cohort had a mean age of 55 years with a slight male predominance (61.2%). The mean follow-up was 4.4 ±
4.5 years post TSS. At 3Y post TSS, forty-five, seventeen and twenty-three participants were classified
as CR, SRA and PRA, respectively. Tumor size at baseline was significantly higher in the PRA subgroup
(maximal diameter 30.3 mm versus 27.6 and 22.7 mm in SRA and CR respectively, p=0.018). Further,
the PRA subgroup was associated with higher Knosp grades (p=0.03), as well as a higher prevalence of
proliferative tumor (55% vs 25% in SRA and 7% in CR, p=0.0036) and of increased ki-67 index (50% vs
33% in SRA and 10% in CR, p=0.02). No single parameter could effectively predict stable disease (CR or
SRA) versus progressive disease (PRA) outcome at three years. Regarding the secondary outcome fifty-
two patients had available follow-up data at 5Y, ten (19%) displayed tumoral progression, of whom six
had CR at 3Y. Fifty-five patients had available follow-up data past five years, fourteen (25%) patients
presented newly progressive disease. Progression at last follow-up was associated with SRA versus CR
status at three years (53% versus 15% respectively, p=0.012).
Conclusion: Tumor size, extension and proliferation are associated with tumor recurrence or regrowth
following TSS. Nevertheless, late progression of NFPA is not an infrequent finding and can occur in
cases with initially complete resection after TSS. The cause remains unclear and the absence of reliable
predictive parameters stresses the need to maintain long-term MRI monitoring.