Study Objectives: Vestibular schwannoma (VS) is a benign tumor in the brain arising from cranial nerve VIII, commonly affecting the internal auditory canal and the cerebellopontine angle. This study evaluates the long-term efficacy and safety of stereotactic radiosurgery (SRS) using CyberKnife, a platform pioneered at Stanford, highlighting our institution’s extensive long-term experience and data.
Methods:
We retrospectively analyzed a total of 344 VS cases treated with CyberKnife SRS from 1998 to 2014. Data included patient demographics, clinicopathology, radiology, and treatment details. Statistical analyses included Chi-square tests, Mann-Whitney U tests, independent t-tests, and Kaplan-Meier analysis.
Study Results:
The median follow-up was 157 months, representing one of the longest follow-up periods reported. The mean age was 51.9 years, with 50.9% female patients. The median tumor size was 1.7 cm, with a median target volume of 0.94 cc. Median maximum and prescribed doses were 22.5 Gy and 18 Gy, respectively. NF2 patients received higher doses (P=0.016) and had longer follow-up (P=0.012). NF2-associated tumors more frequently presented with higher Koos grades and required additional interventions (P=0.025). CN V deficits correlated with CN VIII symptom resolution (P=0.002). Notably, smokers (P=0.001) and non-hypertensive patients (P=0.001) had higher symptom resolution rates. Local recurrence was higher in those with prior surgery (P=0.048). Remarkably, local control rates were 100% at 2 years, 98.8% at 5 years, 94.2% at 15 years, and 89.3% at 25 years. Overall survival was 100% at 10 years and remained at 97.1% at 25 years.
Study Conclusion:
Our extensive long-term data confirm that CyberKnife SRS provides sustained local control and safety for VS treatment over decades, reinforcing its role as a reliable and effective management strategy pioneered at Stanford.
Study Presented by David J. Park, MD, Ph.D., FCNS/ Stanford University School of Medicine · Palo Alto, USA
David J. Park1, Ahed H. Kattaa1, Juan J. Cardona1, Elaheh Shaghaghian1, Amirhossein Akhavan-Sigari1, Shagun Ravi Nasta1, Harini Voruganti1, Isabelle Lee1, Yusuke S. Hori1, Sara Emrich1, Louisa Ustrzynski1, Armine Tayag1, John R. Adler1, Steven D. Chang1
Neurosurgery, Stanford University School of Medicine, Palo alto, USA
- Robotic Precision: The system’s robotic arm moves around the patient to target the tumor from virtually unlimited angles.
- Tumor Tracking: It continuously tracks the tumor and adjusts for tiny patient movements (like breathing), ensuring pinpoint accuracy.
- Fractionation: Unlike some single-session radiosurgery methods, CyberKnife often breaks the treatment into 1 to 5 smaller doses over consecutive days, which helps protect healthy brain tissue and delicate cranial nerves.
- Tumor Control: Studies show a 95% to 99% success rate in stopping vestibular schwannoma growth.
- Hearing Preservation: Serviceable hearing is preserved in about 70% to 80% of patients.
- Nerve Safety: The risk of facial nerve damage (which causes facial paralysis) is very low, typically ranging from 0% to 5%.
- Outpatient Treatment: No incisions, no general anesthesia, and no hospital stay required.
- Recovery: Patients can usually return to their normal daily activities immediately following each session.
- Delayed Results: CyberKnife does not remove the tumor; it kills the cells to stop them from dividing. It can take several months or even years for the tumor to shrink or stop showing growth on follow-up scans.
- Side Effects: While rare, some patients may experience mild fatigue, headaches, temporary dizziness, or a slight increase in tinnitus after treatment.