ESTRO 2021 Abstract Book

S572

ESTRO 2021

Conclusion The proposed ESTRO EORTC OMD classification was successfully applied to a contemporary cohort of OMD patients treated with SBRT. Patients with induced OMD are characterized by significantly shorter OS and PFS compared to patients with de-novo and induced OMD.

J. Willmann and E. Vlaskou Badra contributed equally to this work .

PD-0743 Treatment patterns for adrenal metastases in the era of MR-guided stereotactic ablative radiotherapy C. van Vliet 1 , F. Schneiders 1 , A. Engelsman 2 , S. Hashemi 3 , I. Bahce 3 , C. Haasbeek 1 , A. Bruynzeel 1 , F. Lagerwaard 1 , M. Palacios 1 , A. Becker-Commissaris 3 , B. Slotman 1 , C. Dickhoff 2 , S. Senan 1 1 Amsterdam UMC - location VUMC, Radiation Oncology, Amsterdam, The Netherlands; 2 Amsterdam UMC - location VUMC, Surgery, Amsterdam, The Netherlands; 3 Amsterdam UMC - location VUMC, Pulmonary Diseases, Amsterdam, The Netherlands Purpose or Objective Radical treatment can improve survival in patients presenting with oligometastases. Surgery is an established treatment for adrenal metastases, and high local control rates can be achieved with stereotactic ablative radiotherapy (SABR) when a biological equivalent dose of ≥100 Gy is delivered (Chen WC, IJROBP 2020). Stereotactic MR-guided adaptive radiation therapy (SMART) was introduced at our center in 2016. We studied our institutional referral patterns for adrenal surgery over a 10-year period, and for SMART between 2016- 2019. Materials and Methods Details of all patients referred for radical treatment of adrenal metastases were collected in an ethics- approved institutional database. Details of surgical patients were obtained from medical records, and for completeness, were cross-checked with pathology records. SMART treatments were prospectively registered since 2016. Follow-up details and radiological investigations were obtained from referring hospitals, and from general practitioners if necessary. Results Between 2009-2019, 43 patients (44 tumors) underwent surgery for an adrenal metastasis. Between 2016- 2019, 51 patients (54 tumors) underwent SMART (ViewRay ® Inc MRIdian). The most frequent primary tumor site was lung cancer (75% SMART cohort, 58% surgical cohort). A common presentation in the surgery cohort were patients with solitary adrenal metastases (metachronous 74%, synchronous 23%). The median tumor size was 43 mm, and no patients received concurrent systemic therapy. Laparoscopic resection was performed in 58% of cases, and mean duration of in-hospital-stay was 5 days. Grades 1-2 complications occurred in 16% of patients, and no grade ≥3 complications were recorded. SMART was mainly performed for a metachronous recurrence in the adrenals (in 44%), or for oligoprogressive disease (39%), as an outpatient treatment using 50 Gy (5 fractions) in 74% of patients. Median adrenal tumor size was 29 mm; 11% received concurrent systemic therapy. Acute toxicity grade 1-2 occurred in 59%, mostly fatigue and nausea. Grade 3 nausea was recorded in 1 patient. Median follow up was 21 months for surgery and 16.8 months for SMART. Overall local control rates were 74% (surgery) versus 96% (SMART). Overall survival (OS) and progression-free survival (PFS) rates were not