Therapeutic and prognostic impact of target volume delineation in postoperative radiotherapy for high-grade glioma patients with subventricular zone involvement.

Objective: This study aimed to analyze the effect of target volumes for radiotherapy and dose on the prognosis of high-grade glioma (HGG) patients when the tumor involves the subventricular zone (SVZ), and to provide a reference for postoperative target volume delineation in HGG patients with SVZ involvement.

Methods: The clinical and pathological data were collected from 50 HGG patients with SVZ involvement were collected in the Department of Neurosurgery of the First Affiliated Hospital of Soochow University during the period from January 1, 2017 to December 31, 2020. The average dose (Dmean) of the whole ipsilateral and contralateral SVZs as well as the V45Gy and V60Gy of the whole ipsilateral SVZs of the tumor were derived from the dose-volume histograms (DVH). The Kaplan-Meier analysis was applied to compare the survival differences between groups under different factors. The Cox proportional risk regression model was used to analyze the influencing factors of progression-free survival (PFS) and overall survival (OS). The correlation between the size of the ipsilateral SVZ target area range and the progression pattern was tested by chi-square test.

Results: Univariate analysis revealed that the potential predictors of PFS of HGG patients with tumor involvement in SVZ were as follows: multiple lesions, tumor size > 3.5 cm and total resection; the potential predictors of OS were multiple lesions, surgical approaches to the lateral ventricles and the dose of contralateral SVZ > 37.33 Gy. Multibariate analysis showed that tumor size > 3.5 cm and total resection were the independent prognostic factors of PFS; multiple lesions was the independent prognostic factors of OS. The Kaplan-Meier method showed that the median PFS and OS of HGG patients with V60Gy ≥ 50% was higher than that of patients with V60Gy < 50% but the difference was not statistically significant. Subgroup analysis showed that patients with V60Gy ≥ 50% had significantly higher PFS in the age < 60 years subgroup (P = 0.006), WHO IV grade (P = 0.006), and surgical penetration of the lateral ventricle subgroup (P = 0.034) than in the V60Gy < 50%. Patients with V60Gy ≥ 50% had significantly higher OS in the WHO IV grade subgroup (P = 0.035), surgically penetrated lateral ventricle subgroup (P = 0.008), IDH1 wild-type subgroup (P = 0.012), and MGMT unmethylated subgroup (P = 0.047) than in V60Gy < 50%. A volume of ≥ 50% of the ipsilateral SVZ receiving a 60 Gy irradiation dose improves local control and reduces the risk of local recurrence in patients with SVZ involvement in HGG.

Conclusions: For SVZ-involved HGG patients, the whole ipsilateral SVZ receiving 60 Gy irradiation dose in ≥ 50% of the volume prolonged PFS in those with age < 60 years, WHO IV grade and surgically penetrating lateral ventricles and prolonged OS in those with WHO IV grade, surgically penetrating lateral ventricles, IDH1 wild-type and MGMT unmethylated.