Radiobiology

Zap-X Radiosurgery System: Initial Clinical Experience in a Recurrent Gamma Knife Case Series

INTRODUCTION

The ZAP-X® Gyroscopic Radiosurgery System (ZAP Surgical Systems, Inc., San Carlos, CA, USA) is expected to be a highly accurate next-generation treatment system that enables gyro-stereotactic irradiation of intracranial lesions. In this study, we report the initial treatment course using ZAP-X for intracranial lesions that recurred after Gamma Knife (GK) treatment.

METHODS

Patients with intracranial tumors treated with ZAP-X from April to August 2023 who relapsed after GK therapy were eligible for participating in this study. The primary endpoint was the progression control rate at six months; the secondary endpoints were the rate of target lesion reduction, treatment effect by tumor doubling time (TDT) before ZAP-X intervention, and adverse events.

RESULTS

Six lesions were evaluated in six patients (two meningiomas, one solitary fibrous tumor, one auditory neuroma, one glomus tumor, and one metastatic tumor). The mean follow-up period was 10.6 months after treatment. The mean lesion volume was 5.3 cm3; the mean TDT was 241 days. The six-month progression control rate was 100%, with two partial responses and four stable diseases at the last evaluation. Adverse events were limited to only imaging changes in one patient (16.6%), indicating a significant correlation between ZAP-X pre-intervention TDT and post-intervention reduction rate.

CONCLUSIONS

The initial results of ZAP-X treatment in patients with recurrent disease following GK are reported for the first time. ZAP-X demonstrated potent anti-tumor efficacy and adequate tolerability and should be considered a new treatment option for relapsed refractory patients. Future studies should increase the number of cases and follow-up periods to further evaluate treatment outcomes and adverse events.

Dual-Target Radiosurgery for Concomitant Continuous Pain Presentation of Trigeminal Neuralgia: Radiomodulation Effect and Dose

OBJECTIVES

Patients with trigeminal neuralgia (TN) experience concomitant continuous pain (CCP) that can be difficult to treat. A dual-target approach delivering a high dose of radiation to the nerve and the contralateral thalamus can develop a fast radiomodulation effect on lowering pain. We sought to determine if this effect was dose dependent.

METHODS

We retrospectively reviewed 21 patients treated with radiosurgery in CCP and severe TN pain, with a visual analog scale (VAS) score of nine out of 10 at the time of treatment. Ten patients were treated with a high dose (>120 Gy) in the thalamus 90 Gy to the nerve, and the rest with a low dose (<120 Gy) to the thalamus and >90 Gy to the nerve.

RESULTS

Of those who received the high dose to the thalamus, six patients (60%) received 140 Gy, and four (40%) received 120 Gy, with a median dose to the trigeminal nerve of 90 and 85 Gy, respectively. The high thalamus dose showed a radiomodulation effect from day 1. The low thalamus dose did not produce radiomodulation on any of the first four days. The percentage of VAS score reduction one month after treatment was higher in the high-thalamus dose group than in the low-thalamus dose group. At three months, VAS score was 2 in the high-dose group and 4 in the low-dose group.

CONCLUSIONS

The radiomodulation effect in pain and dual-target radiosurgery is dose dependent in CCP in TN; a high dose can provide a more consistent clinical result than a lower dose.