Immediate Versus Delayed Treatment Does Not Influence Long-term Outcomes After Radiation Therapy for Vestibular Schwannoma

Abstract

Purpose/Objective(s): Observation after detection is now frequently selected as a primary management option for vestibular schwannoma (VS). It is uncertain whether this approach affects patient outcomes. It is possible that patients treated at time of progression are at an increased risk of treatment failure compared to patients treated at the time of initial detection, even among patients who may not have progressed for many years without treatment. In this study, we explore whether the decision for early or delayed treatment impacts treatment success among patients treated with hypofractionated stereotactic radiation therapy (HSRT). Materials/Methods: A retrospective review of 432 VS patients treated with HSRT regimens of 25Gy in 5 fractions or 12-15Gy in 1 fraction was performed. Patients were stratified as: (1) Early (nZ291, 67.4%), patients treated at time of initial presentation and (2) Delayed (nZ141, 32.6%), patients with radiological and/or clinical progression during a period of observation. Continuous data are summarized using median (interquartile range) and categorical data via frequency (percentage). Outcomes were measured from the date of treatment. Results: The median follow-up was 73.3 (48.7-102.9) months in the early group and 61.5 (41.0-88.7) months in the Delayed group. Baseline demographics and median baseline tumor volume (BTV) between the two groups were similar, except for older age at treatment (P 0.05). No significant differences were observed between groups with regards to median tumor volume at last follow-up, treatment failure requiring salvage microsurgery, or rate of clinical/radiological progression after treatment. Of note, a greater reduction in baseline tumor volume was observed in the Delayed group (median: -41.1%, IQR: -66.7% 9.4%) compared to the Early group (median: -32.5%, IQR: -66.7% 11.0%); however, this finding was not significant (P>0.05). Salvage microsurgery was required in 11 (3.8%) patients in the early group and 3 (2.1%) patients in the Delayed group. Ultimately, radiation therapy was equally successful in most patients in both groups (Early: nZ280, 96.2% vs Delayed: nZ138, 97.9%, PZ0.6). Conclusion: We report no difference in treatment failure rates among VS patients treated at time of initial detection versus those treated at time of progression. These data suggest that delaying RT-related toxicity by postponing RT until progression may be a reasonable approach. Author Disclosure: E.W. Sankey: None. A.E. Marciscano: None. I. Jusue-Torres: Research Grant; Salisbury Family Foundation. A. Liu: None. H.W. Francis: None. M. Lim: None. K.J. Redmond: Research Grant; Elekta Ab oligometastases research consortium. D. Rigamonti: Research Grant; Nicholl Family Foundation, Salisbury Family Foundation. L.R. Kleinberg: None.