P14.14.A 3D VOLUME GROWTH RATE OPENS NEW PERSPECTIVES FOR THE CLASSIFICATION OF AGGRESSIVE PITUITARY ADENOMAS

Abstract BACKGROUND WHO 2022 classification of neuroendocrine tumors states that there are currently no grading systems for pituitary adenomas (PitNET). Therefore, we aim to assess three-dimensional volume growth rate (3DVGR) in multiple PitNET and to correlate 3DVGR with tumor progression and neuropathology. MATERIAL AND METHODS Operated patients with growing or proliferative PitNET were retrospectively selected as 10 patients with pituitary metastasis and chordomas. Millimetric gadolinium 3DT1-weighted MRI was requested. RESULTS Totally, 103 3DVGR measurements were performed including 69 non-proliferative and 31 proliferative PitNETs with a median 3DVGR at respectively 21.6 %/year and 49.0 %/year (p<0.0001). Based on ROC analysis (AUC 0.993,p<0.001), we classified 3DVGR in three different classes: 3DVGR<50%/year; 50%/year≤3DVGR<80%/year; 3DVGR≥80%/year with a median PFS at respectively 91.0 months (95%CI: 84.8-107.2), 35.0 months (95%CI: 29.0-35.0) and 7.0 months (95%CI: 4.8-12.2). For 3DVGR<50%/year patients, no significant PFS difference was observed comparing proliferative vs. non-proliferative tumor status (p=0.381). For patients with proliferative status, PFS of patients with 3DVGR≥50%/year was significantly worse than PFS of patients with 3DVGR<50%/year (p<0.001). Finally, by multivariate analysis, only the 3DVGR (cutoff: 50%/year) was significantly associated with the risk of early progression (p<0.001), in contrast to the proliferative status. By combining either the 3DVGR ≥80% or the Ki67 ≥8%, we were able to identify the 12 most aggressive PitNETs, characterized by a dramatic decrease in the median PFS(8.5 months vs. 64 months for the other patients). CONCLUSION PitNET proliferation classification was proposed as follow: 3DVGR<10%: not or slowly progressive; 10%≤3DVGR<50%: slowly progressive; 50%≤3DVGR<80%: rapidly progressive; 80%≤3DVGR: aggressive. Therefore, 3DVGR could be a very interesting tool to assess PitNET proliferation in complement to histological analyses.