Likelihood-of-harm/help im Management von großen Vestibularisschwannomen: Mikrochirurgie versus Radiochirurgie

In large vestibular schwannoma (VS), radiosurgery (SRS) is inferior in respect of tumor control compared to microsurgical resection (SURGERY). However, SURGERY poses a significantly higher risk of facial deterioration in this patient cohort. The aim of this study is to illustrate the effectiveness and harm in terms of Number-Needed-to-Treat/Operate (NNO), Number-Needed-to-harm (NNH), and Likelihood-of-harm/help (LLH) comparing both treatment modalities in large VS.

This is a retrospective dual-center cohort study enrolling consecutive patients with sporadic VS between 2005 and 2011. Tumor size was classified by Hannover Classification. Facial function was reported by House and Brackmann (H&B). Recurrence-free-survival (RFS) was assessed radiographically by contrast-enhanced MR imaging. The absolute risk reduction (ARR) and risk increase (ARI) were calculated as the difference between incidence of recurrences and facial deterioration rates in patients treated with SRS and SURGERY, respectively. ARR and ARI were used to derive additional estimates of treatment effectiveness, i.e. NNO and NNH. LLH was then calculated by a quotient of NNH/NNO to illustrate the risk-benefit-ratio of SURGERY.

N=449 patients treated between 2005 and 2011 met the inclusion criteria. 44% received SURGERY, while N=251 56% received SRS. The overall incidence of recurrence was 9%. The incidence of tumor recurrence was significantly higher in SRS (14%), compared to SURGERY (3%) resulting in ARR of 11% and NNO of 10. Mean follow-up time was 79±53 months in the whole study cohort, with 74±53 months in SURGERY and 82±52 months in SRS. Mean time to recurrence was longer in SURGERY with 102±36 months, compared to 57±36 months in SRS (p=0.007). SURGERY was able to reduce events of recurrence from 55 events per one million patient days to 13. At the same time, SURGERY was related with a significant risk of FFD resulting in a NNH of 12. Overall, LLH calculated at 1.20 was favoring SURGERY, especially in patients under the age of 40 years (LHH=2.40), cystic VS (LLH=4.33), and Hannover T3a (LHH=1.83) and T3b (LHH=1.80).

Due to a poorer response of large VS to SRS, SURGERY is superior in respect of tumor control with an absolute risk reduction of 11% for incidence of recurrence – therefore, one tumor recurrence can be prevented, when 10 patients are treated by SURGERY instead of SRS. LLH portrays the benefit of SURGERY in large VS as well as in in cystic VS and young VS patients.