3D quantitative assessment of response to fractionated stereotactic radiotherapy and single-session stereotactic radiosurgery of vestibular schwannoma

Abstract

Objectives To determine clinical outcome of patients with vestibular schwannoma (VS) after treatment with fractionated stereotactic radiotherapy (FSRT) and single-session stereotactic radiosurgery (SRS) by using 3D quantitative response assessment on MRI. Materials This retrospective analysis included 162 patients who underwent radiation therapy for sporadic VS. Measurements on T1-weighted contrast-enhanced MRI (in 2-year post-therapy intervals: 0–2, 2–4, 4–6, 6–8, 8–10, and 10–12 years) were taken for total tumour volume (TTV) and enhancing tumour volume (ETV) based on a semi-automated technique. Patients were considered non-responders (NRs) if they required subsequent microsurgical resection or developed radiological progression and tumour-related symptoms. Results Median follow-up was 4.1 years (range: 0.4–12.0). TTV and ETV decreased for both the FSRT and SRS groups. However, only the FSRT group achieved significant tumour shrinkage (p < 0.015 for TTV, p < 0.005 for ETV over time). The 11 NRs showed proportionally greater TTV (median TTV pre-treatment: 0.61 cm3, 8–10 years after: 1.77 cm3) and ETV despite radiation therapy compared to responders (median TTV pre-treatment: 1.06 cm3; 10–12 years after: 0.81 cm3; p = 0.001). Conclusion 3D quantification of VS showed a significant decrease in TTV and ETV on FSRT-treated patients only. NRs had significantly greater TTV and ETV over time.

Maximum diameter versus volumetric assessment for the response evaluation of vestibular schwannomas receiving stereotactic radiotherapy

“…Loss of central enhancement was observed in VS after RT [ 13 , 16 , 19 , 20 ], but its clinical significance, especially correlation with tumor shrinkage, has been inconclusive. Schneider et al found that the percentage of enhancing VS volume was nearly constant after gamma knife radiosurgery, but continuously dropped after fractionated stereotactic RT [ 9 ]. Scheller et al [ 20 ] did not found necrotic tumor areas in the operative specimens which had been considered as necrotic tumor areas on MRI.…”

“…Enhanced tumor volume (ETV) within a TV was defined as a hyperenhancing volume in a TV compared to normal tissues. The pons was selected as a reference normal tissue to get a cutoff of hyper-enhancement [ 9 ]. An axial MRI scan of the midlevel of the pons was contoured and a reference plane was produced.…”

Longitudinal Radiographic Outcomes of Vestibular Schwannoma in Single and Fractionated Stereotactic Radiosurgery: A Retrospective Cohort Study

“…The error associated with extrapolated tumor volumes further increases clinical uncertainty regarding postradiosurgical changes. 16,17 For a better understanding of pseudoprogression and longitudinal radiological outcomes after radiosurgical treatment of VS, we retrospective studied patients treated at our institution with either single-fraction SRS or multifraction SRS for VS. In this report, we detail the timing, nature, and frequency of postradiosurgical volumetric changes including pseudoprogression with quantitated tumor volumes obtained by three-dimensional (3D) volumetric analyses.…”

Pretreatment ADC Values Predict Response to Radiosurgery in Vestibular Schwannomas

“…The TTV for each patient was obtained from a previous research project that evaluated the VS volumetrically. 26 The volumetric analysis was performed by a 3D semiautomated quantitative assessment of TTV, and the follow-up was defined as the time from the last radiation therapy session to the date of the most recent MR imaging study obtained in our institution. 26 We also measured the longest dimension of the tumor in axial, craniocaudal, or anteroposterior dimension.…”