Six UK studies investigating stereotactic ablative radiotherapy (SABR) are currently open. Many of these involve the treatment of oligometastatic disease at different locations in the body. Members of all the trial management groups collaborated to generate a consensus document on appropriate organ at risk dose constraints. Values from existing but older reviews were updated using data from current studies. It is hoped that this unified approach will facilitate standardised implementation of SABR across the UK and will allow meaningful toxicity comparisons between SABR studies and internationally.
IntroductionFollowing growing evidence to support the safety, local control (LC) and potential improvement in overall survival (OS) in patients with oligometastatic non-small cell lung cancer (NSCLC) that have been treated with local ablative therapy such as stereotactic ablative radiotherapy (SABR) and stereotactic radiosurgery (SRS), we initiate the SARON trial to investigate the impact and feasibility of adding SABR/SRS and radical radiotherapy (RRT) following standard chemotherapy on OS.Methods and analysisSARON is a large, randomised controlled, multicentre, phase III trial for patients with oligometastatic EGFR, ALK and ROS1 mutation negative NSCLC (1–3 sites of synchronous metastatic disease, one of which must be extracranial). 340 patients will be recruited over 3 years from approximately 30 UK sites and randomised to receive either standard platinum-doublet chemotherapy only (control arm) or standard chemotherapy followed by RRT/SABR to their primary tumour and then SABR/SRS to all other metastatic sites (investigational arm). The primary endpoint is OS; the study is powered to detect an improvement in median survival from 9.9 months in the control arm to 14.3 months in the investigational arm with 85% power and two-sided 5% significance level. The secondary endpoints are LC, progression-free survival, new distant metastasis-free survival, toxicity and quality of life. An early feasibility review will take place after 50 randomised patients. Patients requiring both conventional thoracic RT to the primary and SABR to a thoracic metastasis will be included in a thoracic SABR safety substudy to assess toxicity and planning issues in this subgroup of patients more thoroughly.Ethics and disseminationAll participants are given a SARON patient information sheet and required to give written informed consent. Results will be submitted for presentation at local and international conferences and expected to be published in a peer-reviewed journal.Trial registration numberNCT02417662.Sponsor referenceUCL/13/0594.
Aims: To quantify inter-observer variation between all the intracranial stereotactic radiosurgery (SRS) providers in England in delineating the target volumes of four brain tumour cases. Materials and methods: Twenty-two, cross-platform SRS providers in England were instructed during a national commissioning assessment to contour the gross tumour volume (GTV) of six brain metastases, one cavernous sinus meningioma, one vestibular schwannoma and one pituitary adenoma. An expert reference group provided feedback if submitted contours were considered to be outliers and those centres were instructed to resubmit their contours. All contours were analysed in Python. The target volume contour (observed volume; V OBS ), encompassing volume, 50% agreement volume (AV 50 ), 100% agreement volume (AV 100 ), concordance index (CCI) and discordance index (DCI) were calculated.Results: Twenty-one centres participated using five different treatment platforms (CyberKnife, Gamma Knife, Varian Linac, Elekta Linac, Tomotherapy) and seven different treatment planning systems (GammaPlan, iPlan, Multiplan, Pinnacle, Eclipse, CMS Focal). The greatest variability was observed in the smallest brain metastases (GTV5 AV 50 0.0 cm 3 , CCI 0.28e0.84, DCI 0.00e0.70) and pituitary case (AV 50 1.1 cm 3 , CCI 0.42e0.82, DCI 0.01e0.40). The greatest agreement was observed with the vestibular schwannoma (AV 50 2.8 cm 3 , CCI 0.77e0.94, DCI 0.00e0.17). There were four resubmissions for the cavernous sinus meningioma and three resubmissions for the pituitary adenoma. Conclusions: Inter-observer variability was most evident with the smallest brain metastases and pituitary case. Several additional outliers and one acceptable contour were suggested using the metric-based analysis of AV 50 , CCI and DCI. Comparing contours using these metrics is an effective way to identify whether individual contours are similar to the 'true' target and to flag potentially significant deviations.
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