Abstract Book

S918

ESTRO 37

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. Results 18 patients received SABR with a median age was 69 years (range 58-88). 14 were men and 4 women. The median follow-up was 11 months (9.8-18.4months). The main sites of the primary tumor were: lung with 11 patients, colon and rectum with 5, thymus and soft tissue with 1. The most common histology was: adenocarcinoma in 8 patients, epidermoid 4, leimyosarcoma 1, thymoma 1 and unconfirmed 3. The fractionation more used was 50 Gy / 10Gy / fraction in 6 patients, 60Gy / 12Gy / fraction in 4 patients, 52.5Gy / 7.5Gy / fraction in 2 patients, 54Gy / 18Gy / fraction in 2 patients, 37.5Gy / 5.5Gy / fraction in 2 patients, 44Gy / 12Gy / fraction in 1 patient and 45Gy / 15Gy / fraction in 1 patient. In 88% of the patients, 16 in total, the SABR were performed in lung and in 11% (2 patients) were administrated to the lung and the liver. In 61.1% of the patients (11) the intention of the treatment was radical, 33.3% (6 patients) special palliative and 5.5% (1 patient) rescue. The tumor stage was: 61.1% stage IV, IA 22.2%, IB 11.1%, 5.5% IIIB. The most frequent size was 10-20mm in 8 patients, 30- 40mm in 4, 20-30mm in 3,> 50mm in 3, 0-10mm in 2. The most frequent localization of metastases in lung was: IRL in 6 patients, SRL 5, SLL 3, ILL 3 and in liver segment II 2 patients. At 3 months, 8 patients had stable disease (EE), 4 response partial (PR), 3 complete response (CR), 1 disease progression. At 6 months 6 patients had progressed, 3 in CR, 2 EE and 1 RP. The 77.7% of the patients (14) had no acute toxicity, 22.2% (4) presented different degrees of toxicity (dysphagia G2 1 patient, asthenia G1 1 patient, mild pain 2 patients). 83.3% (15) of the patients did not present late toxicity and only 16% (3) presented G2 pneumonitis. Conclusion The treatment with SABR in patients with metastatic disease seems feasible and similar in terms of local control, without presenting acute and late acute toxicity.

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 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

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)