Pretreatment ADC Predicts Response to Radiosurgery in Solid Vestibular Schwannomas

Objective: Radiosurgery is a well-established treatment option for vestibular schwannomas, but it is often difficult to identify which patients will respond to treatment. Tumor apparent diffusion coefficient (ADC) is a potential marker for predicting tumor control in patients undergoing radiosurgery and for differentiating cases of pseudoprogression from cases of true progression in the early posttreatment period. In this study, we assessed the role of pretreatment and posttreatment ADC in patients undergoing radiosurgery for solid vestibular schwannomas.

Methods: We retrospectively identified patients who underwent radiosurgery for a solid vestibular schwannoma between June 2008 and November 2016 and who had a minimum follow-up of 24 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 also compared between patients with pseudoprogression and those with true progression.

Results: In a total of 58 patients, 45 (77.6%) demonstrated tumor control at final follow-up. Patients with tumor control had significantly higher pretreatment mean (1.75 vs. 1.49; p = 0.014) and maximum (2.35 vs. 1.94; p = 0.017) ADC values than patients with tumor progression. In 21 patients with early posttreatment tumor enlargement, there was no significant difference in pretreatment or posttreatment ADC values between patients with pseudoprogression and those with true progression. The change in ADC values from pretreatment to posttreatment did not differ between patients with tumor control and patients with tumor progression.

Conclusion: Higher pretreatment mean and maximum ADC values predict tumor control in patients undergoing radiosurgery for vestibular schwannomas. Clinicians should consider using ADC to help guide decision-making regarding the treatment of these tumors.

Publication History

Article published online:
12 February 2021