Objectives: Evaluation of the impact of surgical treatment on malignant transformation (MT) of adult supratentorial infiltrative grade II gliomas (G2G) in a series of chemotherapy and radiotherapy-naïve patients.
Background: Despite G2G are slow-growing tumours, they typically undergo MT with a subsequent fatal disease course. An extensive resection alone likely changes their biological behaviour and defers MT; however, this impact is not unequivocally confirmed.
Methods: Thirty-eight chemotherapy and radiotherapy-naïve adult patients operated from 2005 till 2014 for a G2G were investigated. Based on postoperative magnetic resonance imaging (MRI) and/or positron emission tomography follow-up (FU) scans, the patients were classified as "transformers" (15 patients in whom MT occurred during the FU-period) and "non-transformers" (23 patients).
Results: The follow-up period of "non-transformers" was longer (p <0.0001). After adjustment for known risk factors - age, male sex, astrocytoma histology, preoperative tumour volume, preoperative contrast enhancement and positive isocitrate dehydrogenase 1 gene mutation status - a larger log postoperative tumour volume (p=0.031) and a smaller extent of resection (p=0.0086) were associated with a shorter MT-free survival.
Conclusion: In our series, less extensive resections were associated with a shorter time to MT. Our data support an adoption of techniques enabling extensive G2G resections, such as intraoperative imaging and awake resections, into everyday routine (Tab. 1, Fig. 2, Ref. 40).
Keywords: grade II glioma; malignant transformation; prognosis tumour volume.; resection.