ESTRO 2022 - Abstract Book

S524

Abstract book

ESTRO 2022

Materials and Methods The analysis is based on a snapshot of the database on October 1st 2021; results of this abstract are not definitive and updated results will be presented at the conference. A total of n=984 patients were registered of which n=891 were eligible; n=714 were included into this analysis after exclusion of patients with missing data. Results Patients were treated at 31 international centers for oligometastatic breast (n=127), colorectal (n=142), non-small cell lung (n=127) or prostate cancer (n=318). In most patients, oligometastatic disease was characterized by involvement of n=1 organ site (89%) and one solitary metastasis (68.6%). Oligometastatic state was de-novo, repeat or induced oligometastatic disease in 59.9%, 28.7% and 11.4%, respectively. Details of SBRT were available in 612/714 patients for a total of 862 treatments (median 1 per patient, maximum 5). Dose calculation algorithm was Pencil beam in only 6.5%, with all other type B or C. SBRT was performed most often with 5 fractions (40.1%), followed by 3-fraction SBRT (33.9%). Median biological effective dose (BED; a/b ratio 10Gy) prescribed to the CTV/ITV was 72.8Gy with an Q1-Q3 range of 59.5Gy - 107.1Gy. BED doses varied across organ sites with lower doses delivered for spine (median 55.5Gy) and non-vertebral bones (median 60.6Gy) metastases and highest doses delivered for lung (median 134.7Gy) and liver (median 113.1Gy) metastases. Median SBRT doses were 71.5, 79.7 and 87.2 Gy for patients treated for de-novo, repeat or induced oligometastatic disease, respectively. For patients with oligometastatic breast, colorectal, non-small cell lung and prostate cancer, median SBRT doses were 70.3, 120.2, 97.9 and 60.5 Gy respectively. Conclusion A large variation of SBRT doses with respect to fractionation and especially total doses has been observed across primary disease, type of oligometastatic disease and lesion`s organ site. A comprehensive analysis will be presented at the ESTRO conference. Y. Lievens 1 , L. Boesmans 2 , H. Engels 3 , N. Jansen 4 , S. Janssens 2 , V. Remouchamps 5 , S. Roosens 3 , K. Stellamans 6 , D. Verellen 7 , N. Van Damme 2 1 Ghent University Hospital and Ghent University, Radiation Oncology Department, Ghent, Belgium; 2 Belgian Cancer Registry, NA, Brussels, Belgium; 3 Belgian National Institute for Health and Disability Insurance, NA, Brussels, Belgium; 4 CHU de Liège, Radiation Oncology Department, Liège, Belgium; 5 CHU UCL Namur, Site Sainte Elisabeth, Radiation Oncology Department, Namur, Belgium; 6 AZ Groeninge, Radiation Oncology Department, Kortrijk, Belgium; 7 Iridium Netwerk, Antwerp University, Radiation Oncology and Faculty of Medicine and Health Sciences, Antwerp, Belgium Purpose or Objective Stereotactic body radiotherapy (SBRT) has rapidly gained acceptance in the radical treatment of oligometastatic disease (OMD), even if prospective evidence from clinical trials remains scarce and results from randomized phase III trials are still awaited. Patterns-of-care and survival of patients undergoing SBRT for OMD in the context of a coverage with evidence development (CED) program in Belgium are reported. Materials and Methods 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, defined as a maximum of 3 metastatic lesions. ‘Standard’ vs. ‘non-standard’ indications were defined, the latter requiring enrollment in a formal clinical trial to be eligible for registration and financing. 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. Results 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 951. After data cleaning, 5,675 courses concerning 4,841 patients were available for analysis. Of these, 2,790 pertained to OMD, with 1,484 (53%) being ‘standard’ lung metastases, 537 (19%) (para)spinal and 327 (12%) liver metastases. The ‘non-standard OMD’ group included the remaining 442 (16%) courses, with a dominance of lymph node (n=165, 37%) and non-spinal bone (n=248, 56%) metastases. Patients typically had a good performance status and most frequently only one metastatic lesion. Total dose, fractionation and techniques varied, but higher total doses and techniques evaluating/compensating tumor motion were more frequently used for lung and liver metastases than for the other indications. Overall survival was highest in case of ‘non-standard’ metastases, mostly pertaining to patients with primary prostate cancer, whereas liver metastases did worst. Major patient, disease and treatment characteristics, and survival, are shown in table 1; Kaplan-Meyer survival curves in Figure 1. OC-0600 SBRT for oligo-metastatic disease in Belgium: a prospective national registration project.