2613 - Therapeutic and Prognostic Impact of Target Volume Delineation in Postoperative Radiotherapy for High-Grade Glioblastoma Patients with Subventricular Zone Involvement

F. Sun; Department of Radiation Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China/Jiangsu, China

Purpose/Objective(s): 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. Materials/

Methods: The clinical and pathological data of the HGG patients with SVZ involvement were collected in our department during the period from January 1, 2017. The average dose Dmean of the ipsilateral and contralateral SVZs as well as the V45 and V60 of the 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: The quartile doses of the ipsilateral SVZ site of the tumor were 49.76Gy, 55.56Gy and 58.75G; the quartile doses of the contralateral SVZ area were 31.14Gy, 37.33Gy and 45.02Gy. Univariate analysis showed that patients with V60 =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 V60< 50%. Patients with V60 =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 V60<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.
Conclusion: For SVZ-involved HGG patients, 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.