# Prognostic relevance of resection at first recurrence in isocitrate dehydrogenase mutant lower-grade glioma: results from a retrospective, single-center, volumetric analysis

## TL;DR

This study finds that repeat surgery for recurring brain tumors in a specific type of glioma is safe and can improve patient outcomes when the tumor is completely removed.

## Contribution

The study demonstrates that repeat resection at first recurrence in IDH-mutant lower-grade gliomas is associated with prolonged progression-free survival when gross total resection is achieved.

## Key findings

- Repeat resection at first recurrence was associated with prolonged progression-free survival (PFS-2) in IDH-mutant lower-grade glioma patients.
- Gross total resection (GTR) during repeat surgery significantly improved PFS-2 compared to residual tumor volume or non-surgical treatment.
- Functional outcomes remained stable after repeat resection with minimal postoperative deficits.

## Abstract

The prognostic role of repeat resection in IDH-mutant lower-grade glioma remains insufficiently defined. This observational single-center study investigated whether resection at 1st recurrence was associated with (progression-free) survival after recurrence (PFS-2; SAR) and evaluated functional outcomes.

We retrospectively analyzed 148 molecularly characterized IDH-mutant astrocytoma and oligodendroglioma patients, WHO grade 2 and 3, undergoing resection (n = 50) or non-surgical treatment (n = 98) at 1st recurrence between 2001 and 2023. In surgical cases, FLAIR tumor volumes (TV) were assessed volumetrically. Prognostic factors were identified by log-rank tests and multivariable Cox proportional hazards regression. Median follow-up was 140 months.

Female sex (p = 0.005), frontal tumors (p = 0.029) and iterative resections (p = 0.025) were more frequent in surgical patients, while non-surgical patients received more systemic treatment. Functional status (KPS, NANO) and tumor characteristics (histology, WHO grade) were balanced. In multivariable analysis, re-resection was associated with prolonged PFS-2 (p = 0.029, HR = 0.560, 95% CI 0.332–0.944), but not with SAR. In surgical cases, median pre- and postoperative TVs were 19.75 cm3 and 4.545 cm3 (p < 0.00001). PFS-2 was significantly prolonged in patients without (n = 12) compared to surgical patients with residual TV (n = 38; p = 0.022) and all patients with residual disease, including non-surgical cases (n = 136; p = 0.007). Following re-resection, a permanent deficit remained in 1 patient (2%). Functional status was preserved, with stable rates of KPS ≥90% and NANO = 0 at 7 days and 3 months postoperatively.

In this cohort of IDH-mutant lower-grade gliomas, repeat resection at 1st recurrence was safe and associated with prolonged PFS-2, especially when GTR was achieved, supporting its relevance in multimodal treatment.

The online version contains supplementary material available at 10.1007/s11060-025-05353-x.