OS06.4.A NEURO-ONCOLOGICAL SUPERIORITY OF SUPRATOTAL RESECTION AGAINST TOTAL RESECTION FOR IDH-MUTANT LOWER-GRADE GLIOMAS
Authors: Gallotti A L , Rossi M , Conti Nibali M , Sciortino T , Gay L G , Puglisi G , Leonetti A , Bello L 
Published: October 2024

Abstract

BACKGROUND
Lower-grade gliomas (LGGs) are highly infiltrative, intrinsic, IDH-mutant brain tumors affecting the young population, evolving to cause functional impairment till death. Surgical resection is the mainstay of LGG treatment. However, even gross total resection does not prevent them from recurring. This study compares the oncological effect of Supratotal against the gold standard of Total resection for LGGs.

MATERIAL AND METHODS
All LGG patients undergoing surgery according to functional boundaries between 2007 and 2017 were included. Extent of resection was calculated on residual tumor volume (RTV) at MRI: Total (TR, RTV = 0), Subtotal (0 &lt; RTV ≤ 5 mL), Partial (RTV &gt; 5 mL). Supratotal resection (SpTR) was defined as complete removal, with a postoperative cavity larger than the preoperative tumor. Only TR and SpTR were considered. Tumors were classified according to WHO 2021 criteria, recurrence according to RANO.

RESULTS
Out of 614 patients selected, 205 underwent SpTR and 165 TR. Grade 2 tumors and Oligodendrogliomas were associated to SpTR (84.9% and 51.7%), while Grade 3 and Astrocytomas to TR (27.9%, p = 0.004, and 63.0% p = 0.006). Frontal and Temporal locations were more frequent among SpTR, while Insular and Parietal among TR (p = 0.008). Preoperative seizures were associated with SpTR (p &lt; 0.001). No permanent deficits and no postoperative mortality were observed. Recurrences were more frequent after TR (78.2% vs 4.9%, p &lt; 0.001). At Cox regression SpTR showed a protective effect (HR 0.03, p &lt; 0.001), together with Oligodendroglioma (HR 0.60, p = 0.011). Grade 3 was associated with increased recurrence (HR 1.79, p = 0.005).Out of 377 patients with a first recurrence, 101 underwent SpTR and 144 TR. No significant differences were detected in histotype and grade. Local recurrences were more frequently subjected to SpTR (p &lt; 0.001). Second recurrences were more frequent after TR (69.4% vs 5%, p &lt; 0.001). Multiple Cox regression confirmed SpTR protective effect (HR 0.03, p &lt; 0.001), while initial Grade 3 (HR 1.89, p = 0.003) and malignant transformation of recurrence (HR 2.58, p &lt; 0.001) were independent risk factors. SpTR was significantly protective against death after both initial (HR 0.01, p &lt; 0.001) and repeated surgery (HR 0.01, p &lt; 0.001).The PFS effect of SpTR was investigated by propensity score matched analysis, to abate the effects of confounders. SpTR remained significant both initially (HR 0.04, p &lt; 0.001) and at first recurrence (HR 0.05, p &lt; 0.001).

CONCLUSION
This study demonstrates the superiority of SpTR against TR in IDH-mutant lesions in terms of PFS and risk of death in a very large cohort of patients, both at initial surgery and at first recurrence. Initial grade is an independent risk factor both at initial surgery and at recurrence, while histomolecular subtype only at initial surgery. Malignant transformation is an independent risk factor for surgery on recurrences.