Pretreatment ADC predicts tumor control after Gamma Knife radiosurgery in solid vestibular schwannomas



Radiosurgery is a well-established treatment for vestibular schwannomas (VSs), but it is often difficult to identify which tumors will respond to treatment. We sought to determine whether pretreatment or posttreatment tumor apparent diffusion coefficient (ADC) values could predict tumor control in patients undergoing Gamma Knife radiosurgery (GKRS) and whether these values could differentiate between cases of pseudoprogression and cases of true progression in the early posttreatment period.


We retrospectively identified patients who underwent GKRS for solid VSs between June 2008 and November 2016 and who had a minimum follow-up of 36 months. Pretreatment and posttreatment minimum, mean, and maximum ADC values were measured for the whole tumor volume and were compared between patients with tumor control and those with tumor progression. In patients with early posttreatment tumor enlargement, ADC values were compared between patients with pseudoprogression and those with true progression.


Of the 44 study patients, 34 (77.3%) demonstrated tumor control at final follow-up. Patients with tumor control had higher pretreatment minimum (1.35 vs 1.09; p = 0.008), mean (1.80 vs 1.45; p = 0.004), and maximum (2.41 vs 1.91; p = 0.011) ADC values than patients with tumor progression. ADC values did not differ between patients with pseudoprogression and those with true progression at early posttreatment follow-up.


ADC values may be helpful in predicting response to GKRS in patients with solid VSs but cannot predict which tumors will undergo pseudoprogression. Patients with higher pretreatment ADC values may be more likely to demonstrate posttreatment tumor control.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2


  1. 1.

    Boari N et al (2014) Gamma Knife radiosurgery for vestibular schwannoma: clinical results at long-term follow-up in a series of 379 patients. J Neurosurg 121(Suppl):123–142

    Article  Google Scholar 

  2. 2.

    Bowden G et al (2017) Cystic vestibular schwannomas respond best to radiosurgery. Neurosurgery 81(3):490–497

    Article  Google Scholar 

  3. 3.

    Camargo A et al (2017) Pretreatment ADC values predict response to radiosurgery in vestibular schwannomas. AJNR Am J Neuroradiol 38(6):1200–1205

    CAS  Article  Google Scholar 

  4. 4.

    Chuang CC et al (2012) Use of apparent diffusion coefficients in evaluating the response of vestibular schwannomas to Gamma Knife surgery. J Neurosurg 117(Suppl):63–68

    Article  Google Scholar 

  5. 5.

    Elson A et al (2015) Evaluation of absolute and normalized apparent diffusion coefficient (ADC) values within the post-operative T2/FLAIR volume as adverse prognostic indicators in glioblastoma. J Neurooncol 122(3):549–558

    CAS  Article  Google Scholar 

  6. 6.

    Frisch CD et al (2017) Stereotactic radiosurgery for cystic vestibular schwannomas. Neurosurgery 80(1):112–118

    Article  Google Scholar 

  7. 7.

    Guo AC et al (2002) Lymphomas and high-grade astrocytomas: comparison of water diffusibility and histologic characteristics. Radiology 224(1):177–183

    Article  Google Scholar 

  8. 8.

    Hayhurst C, Zadeh G (2012) Tumor pseudoprogression following radiosurgery for vestibular schwannoma. Neuro Oncol 14(1):87–92

    Article  Google Scholar 

  9. 9.

    Huang CF et al (2010) Apparent diffusion coefficients for evaluation of the response of brain tumors treated by Gamma Knife surgery. J Neurosurg 113(Suppl):97–104

    Article  Google Scholar 

  10. 10.

    Johnson S et al (2019) Long term results of primary radiosurgery for vestibular schwannomas. J Neurooncol 145(2):247–255

    CAS  Article  Google Scholar 

  11. 11.

    Khattab MH et al (2020) Longitudinal radiographic outcomes of vestibular schwannoma in single and fractionated stereotactic radiosurgery: a retrospective cohort study. J Neurol Surg B Skull Base 81(3):308–316

    Article  Google Scholar 

  12. 12.

    Kim JH et al (2017) Predictive factors of unfavorable events after gamma knife radiosurgery for vestibular schwannoma. World Neurosurg 107:175–184

    Article  Google Scholar 

  13. 13.

    Klijn S et al (2016) Gamma Knife radiosurgery for vestibular schwannomas: evaluation of tumor control and its predictors in a large patient cohort in The Netherlands. J Neurosurg 124(6):1619–1626

    Article  Google Scholar 

  14. 14.

    Kshettry VR et al (2015) Incidence of vestibular schwannomas in the United States. J Neurooncol 124(2):223–228

    Article  Google Scholar 

  15. 15.

    Mardor Y et al (2004) Pretreatment prediction of brain tumors' response to radiation therapy using high b-value diffusion-weighted MRI. Neoplasia 6(2):136–142

    Article  Google Scholar 

  16. 16.

    Marston AP et al (2017) Pretreatment growth rate as a predictor of tumor control following Gamma Knife radiosurgery for sporadic vestibular schwannoma. J Neurosurg 127(2):380–387

    Article  Google Scholar 

  17. 17.

    Mindermann T, Schlegel I (2014) How to distinguish tumor growth from transient expansion of vestibular schwannomas following Gamma Knife radiosurgery. Acta Neurochir (Wien) 156(6):1121–1123

    Article  Google Scholar 

  18. 18.

    Nagano O et al (2008) Transient expansion of vestibular schwannoma following stereotactic radiosurgery. J Neurosurg 109(5):811–816

    Article  Google Scholar 

  19. 19.

    Ostrom QT et al (2019) CBTRUS statistical report: primary brain and other central nervous system tumors diagnosed in the United States in 2012-2016. Neuro Oncol 21(Suppl 5):v1–v100

    Article  Google Scholar 

  20. 20.

    Plotkin SR et al (2009) Suggested response criteria for phase II antitumor drug studies for neurofibromatosis type 2 related vestibular schwannoma. J Neurooncol 93(1):61–77

    CAS  Article  Google Scholar 

  21. 21.

    Pollock BE (2006) Management of vestibular schwannomas that enlarge after stereotactic radiosurgery: treatment recommendations based on a 15 year experience. Neurosurgery 58(2):241–248 discussion 241-8

    Article  Google Scholar 

  22. 22.

    Sasaki M et al (2008) Variability in absolute apparent diffusion coefficient values across different platforms may be substantial: a multivendor, multi-institutional comparison study. Radiology 249(2):624–630

    Article  Google Scholar 

  23. 23.

    Watanabe S et al (2016) Stereotactic radiosurgery for vestibular schwannomas: average 10-year follow-up results focusing on long-term hearing preservation. J Neurosurg 125(Suppl 1):64–72

    Article  Google Scholar 

  24. 24.

    Wu CC et al (2017) Magnetic resonance imaging characteristics and the prediction of outcome of vestibular schwannomas following Gamma Knife radiosurgery. J Neurosurg 127(6):1384–1391

    Article  Google Scholar 

Download references


The authors sincerely thank Megan Griffiths, ELS, for providing editorial assistance.

Author information



Corresponding author

Correspondence to Varun R. Kshettry.

Ethics declarations

Ethics Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee (name of institute/committee) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. For this type of study, formal consent is not required.

Conflict of interest

All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge, or beliefs) in the subject matter or materials discussed in this manuscript. Non-relevant disclosures include the following: Varun R. Kshettry is a consultant for Integra LifeSciences and Stryker Corporation; Pablo F. Recinos is a consultant for Stryker Corporation.

Additional information

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

This article is part of the Topical Collection on Tumor – Schwannoma

A portion of this work was presented as an oral presentation at the North American Skull Base Society 29th Annual Meeting on February 17, 2019, in Orlando, FL.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Soni, P., Potter, T., Poturalski, M. et al. Pretreatment ADC predicts tumor control after Gamma Knife radiosurgery in solid vestibular schwannomas. Acta Neurochir (2021).

Download citation


  • Acoustic neuroma
  • Apparent diffusion coefficient
  • Gamma Knife
  • Progression
  • Pseudoprogression
  • Radiosurgery