Comparative analysis of plan quality between two SRS systems for stereotactic irradiation in treating Vestibular...

The purpose of this study was to compare plan quality for vestibular schwannoma (VS) between CyberKnife (CK) and ZAP-X.

Thirty VS cases treated with CK were re-planned on CK and newly planned on ZAP-X. Both plans ensured 98% target coverage. The 30 patients were divided into two groups: 15 patients with Koos grade I and II (grade I/II group) and 15 patients with Koos grade III and IV (grade III/IV group). For patients in the grade I/II group, 12 Gy in 1 fraction was prescribed. For those in the grade III/IV group, they received the total dose of 21 Gy in three fractions. The evaluated parameters included the Gradient Index (GI), Paddick Conformity Index (CI), cochlea and brainstem doses, monitor units (MU), and beam-on time (BT).

In the results, ZAP-X achieved lower mean GI in the grade I/II group while CK did better in the grade III/IV group. The mean CI was higher for ZAP-X in both groups, with a significant difference. The mean cochlear and brainstem doses were lower with ZAP-X in the grade I/II group, with a significant difference. In contrast, no significant difference was observed in the grade III/IV group. In both groups, the mean MU was lower for CK, and the mean BT was shorter for CK.

In radiation therapy for VS, ZAP-X can provide a treatment plan comparable to that of CK. Notably, for smaller targets, ZAP-X has the potential to achieve superior treatment planning compared to CK.