Risk Factors for Local Recurrence after Surgical Resection of Spine Schwannomas: Retrospective Analysis of 169 Patients from a Multicenter International Database
Authors: Zamorano Juan , Fehlings Michael , Nater Anick , Tetrault Lindsay , Varga Peter , Gokaslan Ziya , Boriani Stefano , Fisher Charles , Rihnes Laurence , Bettegowda Chetan , Kawahara Norio , Chou Dean 
Published: May 2015

Introduction Schwannomas are benign neurogenic tumors, with a reported annual incidence between 0.3 and 0.5 per 100,000 people, mainly in their 4th and 5th decades, with no gender preference. Together with neurofibromas, they account for up to 30% of all intraspinal tumors. They usually present as a solitary slow-growing oval, lobulated and encapsulated mass, arising eccentrically from the nerve root sheath. Symptoms and signs are related to root and/or cord compression and may slowly progress with tumor growth. Total resection is the gold standard for patients with initial sensory or motor deficits. Local recurrence is reported to be around 5% and it usually occurs several years after the surgery. The objective of this study was to analyze a multicenter database of patients operated for spine schwannomas to identify risk factors for local recurrence. Patients and Methods Retrospective analysis of 169 patients (age > 18 years) from the AOSpine Multicenter Primary Spinal Tumors Database, who underwent surgery for a spine schwannoma (48% female, mean age at diagnosis 46.6 ± 15.31 years, mean follow-up 50.68 ± 39.23 months). Rates of tumor recurrence and time to recurrence were quantified. The predictive value of various clinical factors, including age, gender, tumor size, affected spinal segments, type of surgery, and extent of disease as defined by the Weinstein-Boriani-Biagini (WBB) classification system, was assessed. Descriptive statistics and univariate analysis was performed. Results The mean number of affected levels per patient was 1.85 ± 0.86 and 82.84% of them were located in the mobile spine (41.42% between L1 and L5). According to the WBB classification, 47.12% of the tumors had an intradural extension, while 31.73% were both intra- and extradural and the mean number of affected sectors was 4.49 ± 3.61. Regarding the surgery, 69.75% of the patients had an en bloc resection, mainly via a posterior approach (74.84%). Nine patients experienced local recurrence (5.3%) at a time range of 81 to 1,518 days after the surgery. These patients were on average younger (39.33 ± 15.58 vs. 47.01 ± 15.29), although this relationship did not reach significance (HR = 0.97, p = 0.16). Overall, 13, 10, and 7% of patients with cervical, sacral, and lumbar disease respectively, experienced tumor recurrence compared with 0% of thoracic patients ( p = 0.18). The location of the tumor ( p = 0.25), whether epidural, intradural or both, and the number of WBB sectors involved (HR = 1.03, p = 0.79) were not significantly related to recurrence. The actual size of the tumor was significantly larger in patients with recurrence (6.97 ± 4.66 vs. 3.81 ± 3.34) (HR = 1.16, p = 0.028), with the extent in the cranial-caudal direction posing the greatest hazard (HR = 1.324, p = 0.0018). With respect to surgical technique, patients receiving a complete resection (3.6%) had a significantly lower risk of recurrence than those treated with an intralesional subtotal procedure (13.9%, p = 0.047). Conclusion Local recurrence after schwannoma resection appears to be determined mainly by the size of the tumor and the extent of the surgical resection.