ESTRO 37 Abstract book

S919

ESTRO 37

Purpose or Objective To identify if there are different radiosensitivities between different bacterial strains and between wild type strains and their knock out DNA homologues. Material and Methods

Purpose or Objective To evaluate the outcome of patients treated with stereotactic body radiotherapy (SBRT) for oligometastatic bone disease, in terms of distant progression-free survival (DPFS) and overall survival (OS). Secondary objectives were to appraise toxicity and pain control rates. Material and Methods From September 2012 to September 2017, 50 patients with 62 bone oligometastases were treated using SBRT technique at our center. Median follow-up time was two- years. Response to radiotherapy was analyzed according to RECIST criteria v1.1 and PERCIST criteria. All patients underwent MRI and PETCT scan alternatively, every 6 months, during that period. Pain flare was defined as an increasing of two points in the pre-treatment pain score. Toxicity was registered and graded according to Common Terminology Criteria for Adverse Events (CTCAE) v4.0. The survival analysis was performed using the Kaplan- Meier method. Results Median age was 57.13 years (r: 36-81). Primary tumors were: breast (45%), prostate (19%), lung (14’5%), kidney (6’5%), colon (3’2%) and others (11’8%). Out of the 62 bone metastases, 38 (61,3%) were located in the spine and the outstanding 24 (38,7%) in non-spinal bony locations. SBRT fractionation schemes were 16 Gy in a single fraction for spinal lesions and 22.5 Gy delivered in 3 fractions for flat and long bone metastases. With a median follow-up time of 23’77 months (r: 1-65), local control of the irradiated bone metastases was achieved in 83% of the cases. The two-year overall survival (OS) and distant progression-free survival (DPFS) were 73’5% and 45%, respectively. Median distant progression-free survival averaged 13’3 months (95% CI: 8’9-17’6), and median survival time was 43 months (95% CI: 26’9-59’1). Local response of the irradiated bone metastases was a prognostic factor regarding OS and DPFS. Seventy percent (35) of the patients with complete response at the oligometastatic site/s do not present systemic progression after 2 years of follow-up; whereas 80% (8) and 87’5% (7) of the patients with local progression or partial response of the irradiated bone metastases distantly progressed, respectively. Eighteen percent of patients had pain flare during or after the treatment. Only two patients (3’2%) experienced grade 1 or 2 CTCAE toxicities (dysphagia G1 and anorexia G2, respectively) and no cases of grade ≥3 toxicity were reported. Conclusion The use of SBRT in the treatment of bone oligometastases is effective and safe, with a low toxicity profile. After evaluation with PETCT scan and MRI, the rate of local control at two-years was 83%. Overall survival and distant control rates were highly dependent on the degree of local response of the irradiated bone metastases, which is a prognostic factor to predict systemic relapse. EP-1712 Bacterial Differential Radiosensibility G. Oses Gonzalez 1 , A. Biete 2 , I. Alejo 3 , M. Alvarez 3 , J. Mas 3 1 Clinical hospital of Barcelona, radiation oncology, Barcelona, Spain 2 Clinical hospital of Barcelona, Radioation oncology, Barcelona, Spain 3 Clinical hospital of Barcelona, Microbiology, Barcelona, Spain

Various normal strains have been irradiated of E. coli, P. aeruginosa, K. pneumoniae, S. eureus, S. epidermidis and E. fecalis were irradiated. The RT doses used were 2, 16, 32 and 64 Gy with a control at 0Gy. Five samples were irradiated in a tube at a concentration of 105 UFC / ml. For each dose and each species. Subsequently they have been planted in a petri-agar plate and the colonies counted at 24 and 48h. At the same time an antibiogram has been performed at different doses and antibiotics (ampicillin, gentamicin, ciprofloxacin, amoxicillin- cefuroxime and cotrimoxazole). Results - The knock out strains are more radiosensitive, the graph shows the results obtained in Pseudomonas aeruginosa. At the 16Gy dose, the survival fraction is 91% in the wild type strain and 65% in the knock out strain. This difference decreases progressively until in very high doses (64Gy) it disappears - E. coli, K. pneumoniae, S. aeruginosa and E. epidermidis more radiosensitive and S. aureus, E. faecalis more radioresistant. - In some strains it was not possible to obtain reliable curves - No modification of the antibiogram has been observed with the different doses of radiation Conclusion - Radiosensitivity between bacterial species varies greatly - There are few data in the literature about bacterial radiosensitivity and still less between "wild type"and deficient in mechanisms of DNA repair (knock out) EP-1713 Treatment response assessment using RECIST and toxicity of SABR in extracranial metastatic disease. R. De Haro Piedra 1 , D.M. Muñoz Carmona 1 , J.M. Nieto- Guerrero Gómez 1 , E. Montero Perea 1 , S. Velázquez Miranda 2 , M.J. Ortiz Gordillo 1 1 University Hospital Virgen del Rocío, Radiation Oncology, SEVILLE, Spain 2 University Hospital Virgen del Rocío, Medical Physics, SEVILLE, Spain Purpose or Objective To assess local disease control using RECIST 1.1 criteria and the grade of acute and late toxicity in patients treated with SABR with metastasic disease in different locations. Material and Methods Data from patients treated with SABR were analyzed between January 1, 2016 and October 31, 2017. The final objectives included were local control, acute and late toxicity.