ESTRO 38 Abstract book

S874 ESTRO 38

previously irradiated area). Twelve patients had non-spine bone lesions only, 16 had lymph node metastastes, and two had mixed disease. Patient and tumor characteristics are presented in table 1.

Limitations include small sample size, limited duration of follow-up, and lack of a control arm. Conclusion SABR in 5 fractions appears extremely safe and feasible, resulting in excellent local control but rather limited progression-free survival. Consequently, 30 more patients were included in the second cohort (3 fractions of 10 Gy), now including translational research to tailor future patient selection. Patients with oligometastases should probably not be withheld systemic treatment. EP-1622 Stereotactic Body Radiation Therapy for Oligometastatic Disease: A single-institution experience L.P. Guzman Gomez 1 , J. Luna Tirado 1 , D. Gonsalves Pieretti 1 , A. Ilundain Idoate 1 , M. Montero Feijoo 1 , W.A. Vasquez Rivas 1 , E. Lopez Ramirez 1 1 Hospital Universitario Fundación Jiménez Díaz, Radiation Oncology Department, Madrid, Spain Purpose or Objective To report clinical outcome and treatment-related toxicity of SBRT in the treatment of oligometastatic disease in patients no suitable for surgery or unresectable metastases. Material and Methods Between May 2015 and December 2017, 68 patients with 1-3 inoperable metastases were treated with SBRT. Medical records were retrospectively reviewed. Patients with liver/abdominal lesions were immobilized with Vac- Q-Fix™ Cushions including BodyFix Diaphragm™ for abdominal compression to minimize respiratory organ motion. No abdominal compression was applied to lung patients, in these cases, 4D planning was required. Dose prescription ranged from 27 to 60 Gy in 3 - 8 fractions. In particular, 27 Gy in 3 fractions was prescribed to bone metastases, 60 Gy in 8 fractions to liver lesions, 50-60 Gy in 4 - 6 fractions to lungs lesions and 40-45 Gy in 4 - 6 fractions to adrenal metastases and abdominal lymph nodes. Dose reductions were allowed if judged necessary to cope with organs at risk (OAR) sparing. Treatment was delivered on Elekta Beam Modulator™ linear accelerator, using volumetric modulated arc therapy (VMAT) with 6-10 MV photon beam energy. Daily image guidance (IGRT) was performed by means of CBCT acquisitions prior to each treatment. After conclusion of SBRT, all patients were assessed at 1.5 months and every 3 months during the first year and every 6 months after 1 follow-up year, with a CT scan and/or RM at each follow up. The primary end points were local control (LC) and treatment-related toxicity. Results Sixty-eight patients with 82 total metastases were treated. Median age at treatment was 64 years (ranged, 28-87 years). 67% were men. 82% of patients presented an ECOG performance status 0-1. Primary tumors were 30 GI, 12 lungs, 10 breasts, 7 prostates, 4 gynecological, 2 melanomas, 2 sarcomas and 1 unknown tumor. 52 patients (76%) had a single lesion; the remaining patients had 2-3 lesions. 48% of the lesions were localized in bones; 28.7%

Median follow-up after SBRT was 9 (2 - 14) months. LC at 6 months was 100%. At 12 months, 2 local relapses were observed, both in lesions >4cm. The median PFS was 8 months. There was a significant difference between PFS in patients who received concomitant systemic treatment and those who did not (median 5.8 vs 13.8 months, p = 0.0012) (figure1). No significant difference in PFS between patients with bone and lymph node metastases was observed. There was no grade ≥ 3 toxicity observed. During follow-up, QoL scores didn’t change significantly.