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Stereotactic body radiotherapy (SBRT) is the standard of care for inoperable early-stage non-small cell lung cancer, and is increasingly used to radically treat oligometastatic disease (OMD). Patterns-of-care and survival are reported of primary lung cancer and metastatic lung lesions radically treated with SBRT in a coverage with evidence development (CED) program in Belgium.

As of 2013, Belgian radiation oncology centers delivering SBRT were invited to participate in the prospective 'Innovative Radiotherapy Techniques' registration project, an initiative of the Belgian National Institute for Health and Disability Insurance (NIHDI), in exchange for temporary research funding. Eligible patients belonged to pre-determined target groups receiving SBRT for a primary tumor or for OMD, the latter defined as a maximum of 3 metastatic lesions. Real-life data on patient, disease and treatment characteristics were recorded in a registration module, available as an online application of the Belgian Cancer Registry. Survival was obtained through August 9^th, 2021.

Between 10/2013 and 12/2019, a total of 6,296 SBRT courses were registered in 20 of the 25 radiotherapy centers in Belgium, courses per center ranging between 21 and 953. After data cleaning, 5,675 courses concerning 4,841 patients were available for analysis. 1,160 of these pertained to SBRT for primary lung cancer (20% of total registrations), with clinical stages T1a-cN0 (n=861), T2a-bN0 (n=218) and T3aN0 (n=34), respectively. 464 courses were delivered for OMD NSCLC (8% of total), the most frequently affected organs being lung (n=377), (para-) spinal (n=36) and liver (n=26). OMD in the lung from various primaries was seen in 1,484 courses (26% of total), colorectal (n=472), lung (n=377) and breast (n=87) cancer being dominant. Performance status was good in the majority of patients. OMD patients were typically younger and had more lesions treated per patient. Primary lung tumors in general received a higher total dose. Motion management was identified in almost all lung lesions, and motion compensation strategies werd used in about two thirds of the cases. Overall survival of primary lung cancer and lung metastases was comparable, while OMD NSCLC patients did slightly worse. Major patient, disease and treatment characteristics, and survival are shown in table 1; Kaplan-Meyer survival curves in Figure 1.

To our knowledge, this is the largest national dataset of prospectively collected, registry-based real-world evidence on SBRT for primary lung cancer and metastatic lung lesions. Acquired in the context of a CED program evaluating the implementation of SBRT across Belgium, the data demonstrate a careful selection of patients treated in clinical practice. In spite of the variability in treatment characteristics reflecting real-life practice, survival data conform to those previously reported in the literature.