Resection of vestibular schwannomas after stereotactic radiosurgery: a systematic review

Abstract

OBJECTIVEMultiple short series have evaluated the efficacy of salvage microsurgery (MS) after stereotactic radiosurgery (SRS) for treatment of vestibular schwannomas (VSs); however, there is a lack of a large volume of patient data available for interpretation and clinical adaptation. The goal of this study was to provide a comprehensive review of tumor characteristics, management, and surgical outcomes of salvage of MS after SRS for VS.METHODSThe Medline/PubMed, Scopus, CINAHL, Cochrane Library, and Google Scholar databases were queried according to PRISMA guidelines. All English-language and translated publications were included. Studies lacking adequate study characteristics and outcomes were excluded. Cases involving neurofibromatosis type 2, previous MS, or malignant transformation were excluded when possible.RESULTSTwenty studies containing 297 cases met inclusion criteria. Three additional cases from Rush University Medical Center were added for 300 total cases. Tumor growth with or without symptoms was the primary indication for salvage surgery (92.3% of cases), followed by worsening of symptoms without growth (4.6%) and cystic enlargement (3.1%). The average time to MS after SRS was 39.4 months. The average size and volume of tumor at surgery were 2.44 cm and 5.92 cm3, respectively. The surgical approach was retrosigmoid (42.8%) and translabyrinthine (57.2%); 59.5% of patients had a House-Brackmann (HB) grade of I or II. The facial nerve was preserved in 91.5% of cases. Facial nerve preservation and HB grades were lower for the translabyrinthine versus retrosigmoid approach (p = 0.31 and p = 0.18, respectively); however, fewer complications were noted in the translabyrinthine approach (p = 0.29). Gross-total resection (GTR) was completed in 55.7% of surgeries. Studies that predominantly used subtotal resection (STR) were associated with a lower rate of facial nerve injury (5.3% vs 11.3%, p = 0.07) and higher rate of HB grade I or II (72.9% vs 48.0%, p = 0.00003) versus those using predominantly GTR. However, majority STR was associated with a recurrence rate of 3.6% as compared to 1.4% for majority GTR (p = 0.29).CONCLUSIONSThis study showed that the leading cause of MS after SRS was tumor growth at an average of 39.4 months after radiation. There were no significant differences in outcomes of facial nerve preservation, postoperative HB grade, or complication rate based on surgical approach. Patients who underwent STR showed statistically significant better HB outcomes compared with GTR. MS after SRS was considered by most authors to be more difficult than primary MS. These data support the notion that the surgical goals of salvage surgery are debulking of tumor mass, decreasing compression of the brainstem, and not necessarily pursuing GTR.

Adjuvant stereotactic radiosurgery with or without postoperative fractionated radiation therapy in adults with skull base chordomas: a systematic review

“…This rate is at the higher end of the range reported in the literature for SRS of skull base tumors (5.4%-11.4%). 43 Therefore, close clinical monitoring and imaging surveillance are crucial for early detection and rapid intervention in these patients.…”

Clinical Outcomes of Salvage Microsurgical Resection after Radiation Therapy for Sporadic Vestibular Schwannomas

“…Compared to established literature, the lower odds of gross total resection observed in this cohort may reflect more difficult planes, increased tumor adherence to the nerve and increased sensitivity of the facial nerve to mechanical stimulation. 13 These challenges in tumor dissection in previously radiated patients has been noted by multiple previous studies. 8,11,12 A second important takeaway from this analysis is that previously radiated patients scored worse on preoperative postural stability indices than nonradiated patients.…”

“…8,11,12 Whitmeyer et al note that patients who underwent salvage microsurgery had gross total resection in only 55.7% of cases, and those who had subtotal resection were associated with lower rates of facial nerve injury. 13 In this context, the purpose of this study was to evaluate clinical outcomes after salvage microsurgery for VS treated initially with modern radiotherapy techniques as compared to those treated with primary microsurgical resection.…”

Quantitative Analysis of the Effect of Stereotactic Radiosurgery for Postoperative Residual Cervical Dumbbell Tumors: A Multicenter Retrospective Cohort Study

“…In addition, some hypotheses could be adopted from vestibular schwannoma because of its histological similarity to dumbbell tumor. In vestibular schwannoma, regrowth following SRS has been reported [ 24 , 25 ]. Several hypotheses for regrowth following SRS have been proposed for vestibular schwannoma: (1) radiation-induced tumor swelling, (2) delayed radiation injury, which causes chronic intratumoral bleeding, and (3) a biological response to radiation [ 26 - 29 ].…”