(P 357) RADIATION THERAPY OF EXTREMITY SOFT TISSUE SARCOMAS: A NATIONWIDE COHORT STUDY OF LATE SIDE EFFECTS - TRIAL IN PROGRESS

Objective: Surgery and radiation therapy (RT) are the preferred treatment modalities for extremity soft tissue sarcomas (ESTS). While adjuvant RT has shown a positive impact on local control and survival for high-grade tumors, it might lead to various immediate and late complications, such as edema, pain, chronic infection, tissue induration, decreased range of motion, decreased muscle strength, and fractures. The incidence and severity of late side effects, and their potential association with high radiation doses, are not well documented. To document and report on late side effects a standardized normal tissue atlas is needed. We aim to analyze the correlation of radiation dose to normal tissues and late side effects of ESTS patients.

Methods: All sarcoma patients in Denmark are treated at one of the two sarcoma centers at Aarhus University Hospital or Rigshospitalet/Herlev Hospital in Copenhagen. In 2009, a nationwide Danish Sarcoma Database (DSD) was established, with comprehensive clinical data on all adult sarcoma patients, including histological subtype, date of diagnosis, sex, age, metastasis, tumor size, tumor grade, primary tumor site, surgical margins intention of treatment (curative or palliative), treatment modality, radiation dose and fractionation. Follow-up data include data on recurrence and death. This study includes every adult ESTS patient treated in Denmark between 2009-2018. Patients treated with adjuvant RT will have organs at risk re-delineated on their planning computed tomography scan (CT-scan). We will correlate the radiation dose with late side effects that will be obtained through a questionnaire sent to all surviving patients. The questionnaire will furthermore contain questions regarding quality of life and functionality (Toronto extremity salvage score (TESS)-questionnaire).

Results: At Aarhus University Hospital, 402 patients with ESTS are included in this study, 161 of which had radiotherapy. Baseline characteristics are shown in table 1.

Conclusion: We are planning to expand this study to a population-based Danish cohort. Results of questionnaires are pending. The aim is to use these population-based data to calculate normal tissue constraint models for radiotherapy of patients with ESTS.