Awake surgery for IDH-mutant grade 2 glioma involving the corpus callosum: long-term onco-functional results after callosectomy in 157 consecutive patients.

OBJECTIVE

Because low-grade glioma (LGG) frequently migrates along the white matter pathways, it may involve the corpus callosum (CC) with possible contralateral diffusion. Contrary to glioblastoma, resection of CC invaded by LGG is poorly documented. Here, a unique experience of 157 patients who underwent awake surgery (AS) for an LGG within the CC is reported to investigate the long-term onco-functional results, including return to work (RTW), after completion of callosectomy.

METHODS

Patients who underwent AS with functional-based resection by the author for an isocitrate dehydrogenase (IDH)-mutant grade 2 glioma infiltrating the CC were selected (June 1997 through December 2023). Functional and oncological results were analyzed by comparing totally resected LGG (group 1) versus incompletely removed LGG (group 2).

RESULTS

In total, 231 AS procedures were performed in 157 consecutive patients (85 males [54.1%], mean ± SD age 36.9 ± 10.1 years). Of these procedures, LGG was discovered due to epilepsy in 117 patients (74.5%) (36 incidentalomas). The mean preoperative Karnofsky performance status (KPS) score was 94 ± 6.6, with 128 working patients (81.5%). There were 150 unilateral (95.5%) fronto-cingulo-callosal or parieto-cingulo-callosal or cingulo-callosal gliomas (88 left [56%] and 62 right [39.5%]) and 7 bifronto-callosal gliomas (4.5%). The mean preoperative tumor volume was 57.1 ± 47.8 cm3. One patient (0.63%) had a persistent postoperative (language) impairment. The mean postoperative KPS score was 94.6 ± 6.1, and 96.8% of patients had RTW. The mean extent of resection was 95% ± 7.9%, with 75 (supra)total resections (47.8%) (group 1) and 82 incomplete resections (52.2%) (group 2). The mean postoperative tumor volume was 4.2 ± 8.6 cm3, with a residue involving the CC less frequently than the hemisphere(s) (p < 0.0001). There were 57 IDH-mutated astrocytomas (36.3%) and 100 oligodendrogliomas (63.7%). Twenty-five patients (15.9%) received early adjuvant treatment, and 74 patients (47.1%) underwent subsequent AS. In group 2, preoperatively, there was a higher rate of intractable seizures (p = 0.009) related to a lower mean KPS score (p = 0.0002), with a greater tumor volume (p = 0.023). Unilateral fronto-cingulo-callosal LGGs were resected more completely than other gliomas (p = 0.031). A residue within the CC was correlated with a decreased proportion of reoperation (p = 0.01) and a shorter overall survival (OS) (p = 0.0002). In the full cohort, the mean follow-up was 9.8 ± 5 years, with an OS rate of 80.9% and median OS of 20 years.

CONCLUSION

This is the first surgical experience of LGG involving the CC resected using AS in the molecular era. The results after callosectomy show a great proportion of functional preservation and RTW, with longer OS.