Combination of stereotactic radiotherapy and targeted therapy: patterns-of-care survey in German-speaking countries.

Introduction: Stereotactic body radiotherapy (SBRT) is increasingly used in metastasized patients receiving targeted/immunotherapy. Information on safety and effectivity of concurrent SBRT and targeted/immunotherapy remains limited, resulting in a lack of consensus on treatment strategies. This study aimed to investigate how SBRT-experienced centers in German-speaking countries combine both therapies.
Materials and Methods: Patterns-of-care of combined treatment with SBRT and targeted/immunotherapy were assessed in 27 radiation oncology centers (19 German, 1 Austrian and 7 Swiss centers). A survey was performed to analyze the details of SBRT, SBRT planning and combined modality treatment. Consensus was defined as ≥75% agreement among participants.
Results: Most participants (60%) were university centers. SBRT for oligometastases has been performed since the year 2008 (median, range 1997-2016), since then a median of 140 cases (5-1100) of SBRT have been performed. In all, 67% performed concurrent SBRT and targeted agents. BRAF inhibitors and VEGF/EGFR inhibitors (bevacizumab [90%], erlotinib [11%], sorafenib [19%], lapatinib [4%]) were considered a contraindication. Bevacizumab was never given simultaneously with SBRT; other agents were given concurrently in 7-52% of centers. A majority (59%) paused targeted agents 1 week before/after SBRT. Only 1 center reduced SBRT dose when combined with targeted agents.
Conclusion: Although evidence for safety and efficacy of concurrent SBRT and targeted agents is limited, it is regularly performed outside of clinical trials. The survey showed consensus not to combine SBRT with antiangiogenic agents, especially bevacizumab. Furthermore, SBRT with concurrent BRAF inhibitors should be practiced with caution and BRAF inhibitors should be paused at least 1 week before SBRT.