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

• Published in: Acta neurochirurgica Vol. 163; no. 4; pp. 1013 - 1019
• Main Authors: Soni, Pranay, Potter, Tamia, Poturalski, Matthew, Karakasis, Christopher, Borghei-Razavi, Hamid, Recinos, Pablo F., Kshettry, Varun R., Lee, Jonathan
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01-04-2021; Springer Nature B.V
• Subjects: Brain cancer; Diffusion coefficient; Interventional Radiology; Medicine; Medicine & Public Health; Minimally Invasive Surgery; Neurology; Neuroradiology; Neurosurgery; Original Article - Tumor - Schwannoma; Radiosurgery; Surgical Orthopedics; Tumor – Schwannoma; Tumors; Vestibular system; Progression; Gamma Knife; Pseudoprogression; Acoustic neuroma; Radiosurgery; Apparent diffusion coefficient
• ISSN: 0001-6268; 0942-0940
• DOI: 10.1007/s00701-021-04738-x

Background
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.
Methods
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.
Results
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.
Conclusions
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.