ESTRO 2020 Abstract book

S650 ESTRO 2020

same dosimetric coverage in the area of treatment as HDR brachytherapy with Iridium 192 with a marked reduction in the dose of organs at risk. PO-1145 Radiotherapy-induced changes in lymphocytes count important for immunotherapy of uterine cancers K. Holub 1,2 , G. Louvel 2 1 Universitat de Barcelona- Hospital Clínic, Radiation Oncology, Barcelona, Spain ; 2 Gustave Roussy, Radiation Oncology, Villejuif- Paris, France Purpose or Objective Although the chemotherapy-induced depletion of circulating white blood cells (WBC) is well recognised, the impact of exclusive radiotherapy (RT) on different subpopulations of WBC remains unexplored. However, this may be of interest for an implementation of immunotherapy based on the immune checkpoint inhibitors in combination with RT in many cancer settings, but especially in endometrial (EC) and cervical cancer (CC), both characterized by a high mutational burden and usually treated with RT or CRT. Material and Methods We compared the differences between pre- and post- treatment WBC mean values in two retrospective cohorts of EC and CC patients (p) treated with cisplatin-based chemoradiation (CRT) or exclusive RT (mean dose external RT 46Gy+/-brachytherapy 10Gy) in a large European centre from 2009 to 2016. A total of 202 consecutive patients with uterine cancers staged FIGO I-IV at diagnosis and with available basal and post-treatment blood tests were evaluated. Patients who presented basal cytopenia or received treatment for cytopenia were excluded. EC and CC patients were analysed separately and as an entire cohort of EC or CC. The analysis was performed using two- sided T-test for paired samples, X2 Pearson test, p-value <0.05 was considered as statistically significant (SPSS v.23). Results In the cohort of 63p with EC, 29p were treated with CRT and 34p underwent exclusive RT. In the cohort of 139p with CC, 105p received CRT and 34p exclusive RT. There were no significant differences between RT and CRT cohort concerning basal WBC levels, as well as mean and median values of WBC in both cancer settings. Both in CC and EC patients, CRT affected significantly all WBC subtypes. The only subtype of WBC depleted after exclusive RT were lymphocytes (p=0.000). Conclusion The selective depletion of lymphocytes after RT is important for immunotherapy with checkpoint inhibitors administrated after RT and CRT. These findings.may suggest that RT promotes recruitment of T cells within the tumour microenvironment producing their depletion in peripheral blood. Our results are of interest for the further research and should be applied in the design of clinical trials with immunotherapy for uterine cancers. PO-1146 Evaluation of Dose to pelvic lymphnodes in CT- based High DoseRate Brachytherapy in Carcinoma Cervix S. Mitra 1 , A. Dewan 2 , S. Aggarwal 3 , I. Singh Wahi 3 , S. Barik 4 , K. Dobriyal 5 , J. Mukhee 5 , H. Khurana 6 1 Rajiv Gandhi Cancer Institute & Research Centre, Senior Consultant Radiation Oncologist, Rohini- Delhi, India ; 2 Rajiv Gandhi Cancer Institute & Research Centre, Consultant Radiation Oncologist, Rohini- Delhi, India ; 3 Rajiv Gandhi Cancer Institute & Research Centre, Attending Consultant Radiation Oncologist, Rohini- Delhi, India ; 4 Rajiv Gandhi Cancer Institute & Research Centre, Senior Resident Radiation Oncologist, Rohini- Delhi, India ; 5 Rajiv Gandhi Cancer Institute & Research Centre, Resident Radiation Oncologist, Rohini- Delhi, India ; 6 Rajiv Gandhi Cancer Institute & Research Centre, Research asisstant, Rohini- Delhi, India

almost equivalent or greater than the cost of primary treatment within our subsidized institutional healthcare system. Conclusion Late radiation toxicity resolves within 12 months in >50% of patients. Patients with residual symptoms of late toxicity at 12 months are likely to have persistent symptoms or progression to higher grade and symptoms are less likely to resolve even with multiple interventions. The direct financial impact is substantial. Structured strategies for management of persistent late toxicities should be developed and investigated. PO-1144 Adjuvant electronic brachytherapy for patients with endometrial cancer. M. Cerrolaza 1 , A. Campos 1 , A. Méndez 1 , M. Gascón 1 , A. Miranda 1 , S. Flamarique 1 , S. Lozares 2 , V. Navarro 1 , R. Ibañez 1 1 Hospital Universitario Miguel Servet, Servicio de Oncología Radioterápica, Zaragoza, Spain ; 2 Hospital Universitario Miguel Servet, Servicio de Radiofísica, Zaragoza, Spain Purpose or Objective Brachytherapy plays a fundamental role in the adjuvant treatment of endometrial cancer as almost every recurrence appears in the vaginal cuff. Traditionally HDR intracavitary brachytherapy with Iridium 192 had been used for this use, but the recent development of electronic brachytherapy based on X-ray emissions has important advantages over this one. Our main objective has been to know the local control of electronic brachytherapy (EBT) in endometrial cancer, to know the toxicity profile and to compare with series from the literature with HDR IR-192 brachytherapy. Material and Methods 193 patients with endometrial cancer were retrospectively analyzed from September 2015 to May 2019 treated with electronic brachytherapy at the Miguel Servet University Hospital. The total dose was 15 Gy in 3 fractions or 14 Gy in 2 for brachytherapy complementary to external radiotherapy; and 25 Gy in 5 fractions or 21 Gy in 3 fractions for exclusive brachytherapy. Acute and late toxicities were recorded by CTCAE v 4.0 criteria. Results The average age of the patients at diagnosis was 66.8 years and 74% diagnosed as endometrioid carcinoma (Type I). According to the FIGO classification, 38% were FIGO IB and the majority histopathological differentiation Grade was grade 2 with 40% observed. Some type of lymphadenectomy performed in 60% of the patients and 34% received adjuvant chemotherapy and 56% external radiotherapy. Mucosal toxicity was observed in 33.68% of the patients, urinary toxicity in 11.4% and rectal toxicity in 14%. All of them were Grade 1 toxicities except in 2 patients who presented Grade 2 acute mucosal toxicity (1%) and in 4 patients late complications Grade 3. Statistically significant association was found only with the rectal toxicity observed at the external beam radiotherapy treatment (p = 0.008). 13.5% of the patients (n=20) had locoregional recurrence and 20 patients distant recurrence. The median follow-up was 19 months and in that time, 15 patients died (8%). The results show an increase in acute grade 1 vaginal mucosal toxicity in our study respect HDR Ir-192 brachytherapy (32% vs 15.8%), but with a decrease in acute grade 2 toxicity (1% EBT, 4.8% Ir-192) and almost absolute reduction of late vaginal mucosal toxicities (1% EBT, 23% Ir-192). The figures of vaginal vault recurrence and the death rate were concordant with the literature. Conclusion Electronic brachytherapy at endometrial cancer is a feasible alternative to HDR brachytherapy with Iridium 192 in effectiveness with an acceptable grade 1 acute toxicity. It has given long-term benefits for patients, providing the