Outcome and toxicity analysis of single dose stereotactic radiosurgery in vestibular schwannoma based on the Koos grading system

Abstract

Stereotactic radiosurgery (SRS) has evolved as widely accepted treatment option for small-sized (Koos i up to ii) vestibular schwannoma (VS). for larger tumors (prevalent Koos Vi), microsurgery or combined treatment strategies are mostly recommended. However, in patients not suited for microsurgery, SRS might also be an alternative to balance tumor control, hearing preservation and adverse effects. The purpose of this analysis was to evaluate the efficacy and toxicity of SRS for VS with regard to different Koos grades. All patients with untreated VS who received SRS at our center were included. outcome analysis included tumor control, preservation of serviceable hearing based on median pure tone averages (ptA), and procedure-related adverse events rated by the common terminology criteria for Adverse Events (CTCAE; v4.03) classification. In total, 258 patients (median age 58 years, range 21-84) were identified with a mean follow-up of 52 months (range 3-228 months). Mean tumor volume was 1.8 ml (range 0.1-18.5). The mean marginal dose was 12.3 Gy ± 0.6 (range 11-13.5). The cohort was divided into two groups: A (Koos grades i and ii, n = 186) and B (Koos grades III and IV, n = 72). The actuarial tumor control rate was 98% after 2 years and 90% after 5 and 10 years. Koos grading did not show a significant impact on tumor control (p = 0.632) or hearing preservation (p = 0.231). After SRS, 18 patients (7%) had new transient or permanent symptoms classified by the CTCAE. The actuarial rate of ctcAe-free survival was not related to Koos grading (p = 0.093). Based on this selected population of Koos grade iii and iV VS without or with only mild symptoms from brainstem compression, SRS can be recommended as the primary therapy with the advantage of low morbidity and satisfactory tumor control. The overall hearing preservation rate and toxicity of SRS was influenced by age and cannot be predicted by tumor volume or Koos grading alone.

Vestibüler Şıvannomlarda Koos Sınıflaması ile ADC- Post Kontrast Sinyal İntensite Değerlerinin İlişkisi

“…Therefore, MRI plays a big role for guidance the surgery. Koos classification has been widely adopted in terms of surgery and has been the subject of many clinical-surgical correlation studies [7,9,12,13]. Although the classification is completely based on radiologic featured, there are not many radiological studies on this subject.…”

“…Koos et al had classified these tumors based on hearing protection after surgery and also defined subgroups according to the position of the cochlear nerve and evaluated the neurotopographic response [7]. Reliability [8], validity [8], response to stereotactic radiosurgery and radiotherapy according to this classification [9,10] were previously evaluated. Reliability of apparent diffusion coefficient (ADC) and signal intensity (SI) according to tumor grade have not been well studied.…”

Stereotactic Radiosurgery for Vestibular Schwannomas: Reducing Toxicity With 11 Gy as the Marginal Prescribed Dose

“…According to published studies, we additionally defined tumor control as freedom from reintervention (repeated SRS or surgery) (18). All these criteria enable to take into account a known transient enlarge of tumor after SRS (19). Clinical treatment-related toxicities were defined as new neurological deficits occurring after SRS.…”

The Relevance of Biologically Effective Dose for Hearing Preservation After Stereotactic Radiosurgery for Vestibular Schwannomas: A Retrospective Longitudinal Study

“…Among benign tumors, SRS for VSs has the largest body of evidence, particularly with regards to tumor control, hearing preservation, and cranial nerve outcomes in general. [9][10][11][12] With regards to SRS, physical dose prescription has been considered the gold standard treatment approach for the past 6 decades. For VSs, there has been a dose de-escalation during time, 10 which had led to similar tumor control, while decreasing the risk of facial palsy to less than 1% in modern series and increasing the probability of hearing preservation.…”

“…Among benign tumors, SRS for VSs has the largest body of evidence, particularly with regards to tumor control, hearing preservation, and cranial nerve outcomes in general. 9-12…”