Article
Microsurgery and CyberKnife radiosurgery in recurrent brain metastases: a comparative study
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Published: | June 18, 2018 |
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Objective: Local treatment concepts are in high demand in the salvage treatment of recurrent brain metastases. Still, their risks and benefits are scarcely characterized. In this retrospective study we analysed the outcome and risk-/benefit-ratio of salvage open tumor resection (OTR) and salvage CyberKnife radiosurgery in the treatment of recurrent brain metastases.
Methods: Thirty-six patients with recurrent intracranial disease, a multimodal pretreatment and a Karnofsky performance score≥ 70 were investigated. Patients underwent either OTR or CyberKnife radiosurgery (single-fraction, reference dose: 17-22 Gy) in two different study centers. Endpoints were the postrecurrence survival (PRS) after salvage treatment as well as tumor control rates. Additionally, both surgical morbidity and CNS toxicity of salvage CyberKnife radiosurgery was assessed.
Results: The CyberKnife cohort (n=21) and the OTR cohort (n=15) were homogenous regarding their demographic parameters except for tumor volume (smaller volume in the CyberKnife cohort: 4 cm3 vs. 8.1 cm3, p=0.009), location and quantity. In 10/15 (21/21) patients from the OTR (CyberKnife) cohort there was a history of whole brain radiotherapy prior to salvage treatment. All patients in the OTR cohort had a history of primary OTR. A significant difference of PRS and local tumor control rates in favor of CyberKnife radiosurgery vs. OTR was observed (p= 0.023 and p=0.0005 respectively). The hazard ratio OTR/CyberKnife was 1.94 (95% CI: 0.75-5.0). In the multivariate analysis, large tumor volume was a significant prognostic factor for worse PRS. Two patients of the CyberKnife cohort with upper-range cumulative dose values suffered from RTOG/EORTC grade I/II toxicity. One patient from the OTR group suffered from a transient visual field defect after tumor removal in the occipital lobe.
Conclusion: Differences in the tumor volume between the two treatment cohorts hamper an in-depth comparative analysis. Still, this study could identify large tumor volume as a strong prognostic factor for poor PRS. Thus, in small-volume recurrent brain metastases, CyberKnife should be clearly preferred over OTR (not only due to its lesser burden of treatment). The favorable risk-/benefit-ratio -especially regarding low radiotoxicity rates in CyberKnife- points to a pro-active therapeutic strategy based on an appropriate patient selection instead of therapeutic nihilism.