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ESTRO 37

to supraclavicular nodes – 1 patient; IIIB – 32 of 46 patients (70%), in this group metastases to paraaortic nodes were found in 10 patients, to supraclavicular nodes – 2 patients, to inguinal nodes – 1 patient). There were 4 patients with non-nodal distant metastases in the group of node-positive FIGO IIIB patients (to bones, lungs, liver). There were no non-nodal distant metastases among FIGO IIB patients nor node-negtive FIGO IIIB patients. Conclusion The rate of nodal metastases in FIGO IIIB is higher than in FIGO IIB. Non-nodal distant metastases were found only in node-positive FIGO IIIB patients. The data have an influence on therapeutic decisions - escalation of EBRT doses to metastatic lymph nodes or further investigation and palliative chemotherapy for (confirmed) distant metastases. EP-1526 IMRT boost in cervical cancer: is it a feasible alternative when Brachytherapy is not practicable? R. Lazzari 1 , G. Riva 1 , O. Alessandro 1 , C.M. Francia 1 , M. Augugliaro 1 , R. Damaris Patricia 1 , A. Vavassori 1 , R. Spoto 1 , S. Comi 2 , F. Cattani 2 , R. Orecchia 3 , B.A. Jereczek- Fossa 1 1 Istituto Europeo di Oncologia - IEO, Radiotherapy, MIlan, Italy 2 Istituto Europeo di Oncologia - IEO, Medical Physics, MIlan, Italy 3 Istituto Europeo di Oncologia - IEO, Scientific Directorate, MIlan, Italy Purpose or Objective Standard treatment in locally advanced cervical cancer is External Beam Radiotherapy (EBRT) concomitant to platinum based chemotherapy, followed by intracavitary/interstitial brachytherapy (BRT). We questioned whether an Intensity Modulated Radiation Therapy (IMRT) boost is safe and feasible in patients clinically or radiologically unfit for a brachytherapy boost. Material and Methods We retrospectively analyzed 23 women (median age 54.9 years, range 29.3 – 81.6) with cervical cancer who underwent EBRT to pelvis ± lombo-aortic lymph nodes and sequential IMRT boost with BrainLab VERO® between July 2014 and January 2017. Patients were evaluated unfit for BRT because of technical limitations, comorbidity or poor compliance. Clinical International Federation of Gynecology and Obstetrics (FIGO) Stages I, II, III, and IV was present in 4%, 39%, 13%, and 44% patients, respectively. Pre boost MRI was performed in all but one patients, Clinical Target Volume (CTV) drawn considering the initial extent of the disease and Planning Target Volume (PTV) achieved adding 3-5 mm to CTV. Constraints to organs at risk were borrowed from the BRT ones. Image Guided Radiotherapy (IGRT) was performed at every fraction in all patients . Toxicity, local relapse rate, local control (LC) and overall survival (OS) were assessed. Acute and late toxicity were evaluated by CTCAE Version 4.1. Results Median follow-up was 17.1 months (4 – 56.6 range). Boost treatment was homogeneously performed to a total dose of 25 Gy in 5 fractions (alternating days). According to CTCAE scoring criteria 10 patients experienced gastrointestinal and genitourinary grade 1-2 acute toxicity (within 6 m.) Grade 2 rectal late toxicity requiring laser-coagulation was registered in 2 patients, no grade > 1 genitourinary late toxicity was observed.

There were no grade 3 or 4 acute or late toxicities. Local relapse (LR) occurred in 4 patients (17%), 6 (23%) experienced distant progression (a patient had both). LR occurred in the patients with following FIGO stages: 2 patients - IIB, 1 patients - IIIB and 1 patients - IVB. At 2 years LC and OS were 77% and 80%, respectively. At the time of assessment, 14 women are alive with no evidence of disease, 2 are alive with disease, 4 died of progressive disease and 2 are lost to follow-up. Conclusion Our preliminary data show the safety and feasibility of IMRT boost in terms of acute and late toxicity. LC and are coherent to the cohort of patients (48% of stage IV disease). IMRT boost seems to be a safe and reasonable alternative when brachytherapy is not practicable. EP-1527 Targeting CXCL12/CXCR4 to enhance the therapeutic ratio during radiochemotherapy for cervix cancer M. Lecavalier-Barsoum 1 , N. Chaudary 2 , P. Thapa 3 , M. Larsen 4 , M. Pintilie 5 , K. Han 6 , R.P. Hill 7 , M. Milosevic 6 1 Jewish General Hospital, Radiation Oncology, Montreal, Canada 2 Princess Margaret Cancer Centre, Research- Radiation Oncology, Toronto, Canada 3 Princess Margaret Cancer Centre, Research, Toronto, Canada 4 MBed Pathology, Pathology, Toronto, Canada 5 Princess Margaret Cancer Centre, Biostatistics, Toronto, Canada 6 Princess Margaret Cancer Centre/ Radiation Medicine/ Medical Sciences, Radiation Oncology/ University of Toronto, Toronto, Canada 7 Princess Margaret Cancer Centre/Radiation Medicine/University of Toronto, Research- Radiation Oncology/Medical Biophysics, Toronto, Canada Purpose or Objective The CXCL12/CXCR4 pathway is upregulated during radiochemotherapy (RTCT) for cervical cancer and contributes to treatment resistance and metastases. We have previously shown that the CXCR4 inhibitor Plerixafor (AMD3100) administered concurrently during RTCT enhanced primary tumor growth delay and reduced lymph node metastases. This study examined the curative potential of RTCT + concurrent Plerixafor; different ways of sequencing RTCT + Plerixafor to maximize efficacy; biomarkers of response to RTCT + Plerixafor; and acute, sub-acute and late intestinal toxicity. Material and Methods Orthotopic cervical cancer xenografts derived from our patients were treated with RT (30 Gy or 50 Gy; 2 Gy/daily) and weekly cisplatin (4 mg/kg), with or without Plerixafor (5 mg/kg/day). Plerixafor was administered concurrently with RTCT for 3 weeks, adjuvant after RTCT for 3 weeks or continuously (concurrent and adjuvant) for 6 weeks and monitored for response. In another experiment, tumor biomarkers of response were evaluated immediately after 30 Gy concurrent treatment. Acute intestinal toxicity was assessed using the gut colony assay, while sub-acute (30 days post-RT) and late (90 days post-RT) intestinal toxicity were assessed histologically using a previously validated intestinal radiation injury scoring system. Results The combination of RTCT (30 Gy) and Plerixafor produced substantial tumor growth delay compared to RTCT alone regardless of sequencing. However, continuous and adjuvant Plerixafor were associated with significantly