Abstract Book

S827

ESTRO 37

longer growth delay than concurrent Plerixafor. With a higher RT dose of 50 Gy to more closely approximate the clinical environment, tumor cure was achieved with RTCT + concurrent Plerixafor. Tumor biomarker assessment at the end of RT (30 Gy) or RTCT alone showed higher CXCL12 and pCXR4 levels and a higher concentration of tumor infiltrating, Ly6G-expressing myeloid derived suppressor cells (MDSCs), consistent with treatment- induced pathway upregulation and MDSC chemotaxis. The addition of Plerixafor abrogated both of these effects. Plerixafor was also associated with reductions in pAKT and pERK, in keeping with direct effects on downstream intracellular signalling pathways. In the acute intestinal toxicity study, a higher level of surviving crypt cells was observed with the addition of Plerixafor to RT or RTCT compared to RT or RTCT alone, suggesting a protective effect. Sub-acute intestinal toxicity was similar between treated arms, but late intestinal toxicity was lower in the RTCT + Plerixafor arm compared to the RT and RTCT arms, again suggesting a protective effect of Plerixafor. Conclusion Adding Plerixafor to RTCT enhances the response of cervical cancer PDX models, blunts treatment-induced upregulation of the CXCL12/CXCR4 pathway and might have protective effect on the intestinal tract. Translation of these findings to phase I/II clinical trials is promising in cervical cancer. Lecavalier-Barsoum and Chaudary contributed equally EP-1528 Evolution of acute toxicities in Volumetric Modulated Arc Therapy of uterine cervix cancer K. SRI HARSHA 1 , S. Saikumar 1 , V. Niranjan 1 , K. Ajay S 1 , P. Kannan 1 , S. Mourougan 1 , P. Jagadesan 1 1 JIPMER, Department of Radiation Oncology, Puducherry, India Purpose or Objective To evaluate the occurrence of acute gastrointestinal, urinary, dermatologic and hematologic toxicities in patients of carcinoma cervix treated with radical concurrent chemo-radiotherapy (CCRT) using Volumetric Modulated Arc Therapy (VMAT). Material and Methods Thirty-six patients of carcinoma cervix FIGO stage IB2-IVA have been prospectively studied during the course of their treatment with radical concurrent chemo-radiation using VMAT. The patients were treated to a total dose of 50.4 Gy in 28 fractions along with once weekly Cisplatin (40 mg/sq.m) followed by 3 sessions of brachytherapy, delivered one week apart to a dose of 8Gy to point A each. The gastrointestinal, urinary, dermatologic and hematologic toxicities were evaluated weekly during the external beam irradiation (EBRT) and also at the end of brachytherapy schedule. The toxicities were graded using Common Terminology Criteria for Adverse Effects version 4(CTCAE v4). The data analysis was done by SPSS version 20. Results The median age at presentation is 52 years. Around 58.3% of the patients had FIGO stage IIB followed by Stage IIIB (30.6%). 7 patients (19.4%) had hemoglobin level <10mg/dl at baseline before starting radiotherapy. Out of the 36 patients studied, the proportion of patients developing ≥ grade 2 acute toxicities (CTCAE grading) anemia, leucopenia, neutropenia and thrombocytopenia were 25%, 8.3%, 5.6% and 0% respectively. The proportion of patients developing ≥ grade 2 acute dermatitis, vomiting, diarrhea, proctitis and cystitis were 5.6%, 2.8%, 22.2%, 2.8% and 0% respectively. Notably, there were no

grade 3 or 4 acute reactions in any of the toxicities studied except grade 3 neutropenia in 1 patient. Most commonly observed toxicity in the first week was vomiting while dermatitis was the most common one in the second, third, fourth and fifth week of EBRT. Highest grade of toxicity noted during chemo-radiation was grade 3 neutropenia, seen in one patient at the fifth week of external beam radiotherapy. The toxicities that appeared right from the first week were vomiting and diarrhea. Many patients developed diarrhea (33.3%) and proctitis (22.2%) only in the last two weeks of EBRT while more cystitis (30.5%) was noted at the end of EBRT and during brachytherapy. Conclusion The present study suggests that concurrent chemo- radiation using VMAT has an excellent acute toxicity profile in the treatment of carcinoma cervix with no grade 3 gastrointestinal, urinary and dermatologic reactions. EP-1530 Dosimetric comparison of MR, MR and Interstitial needles and CT guided brachytherapy in cervical cancer A. Sarwar 1 , N. Lalli 1 , G. Eminowicz 1 1 University College Hospital, Radiotherapy Department, London, United Kingdom Purpose or Objective MR guided brachytherapy (BT) ensures accurate target volume delineation and is essential for accurate cervical BT delivery. Its importance has been identified and forms part of the GEC ESTRO recommendations. Interstitial BT can achieve better target volume coverage where standard applicators fail, particularly in cases with extensive parametrial invasion. Optimal imaging with MR and the use of interstitial needles, we hypothesise, will improve dose distribution to the target volume and avoid OARs. We therefore compared the dosimetric variation achieved with CT guided HDR BT versus MR guided HDR BT with and without interstitial needles. Material and Methods A retrospective dosimetric analysis of 30 cervical cancer patients treated with HDR BT between 2016-2017 was undertaken; 10 CT planned, 10 MR and 10 MR with interstitial needles. All patients were treated with EBRT (50.4 Gy in 28 fractions) followed by BT (21 Gy in 3 fractions). Data was collated from the Oncentra planning Of the 10 patients treated with CT guided BT, 7 had stage 1 or 2 and 3 had stage 3 or 4 disease. For the MR guided cohort, 5 were stage 1 or 2 and 5 were stage 3 or 4 and MR with needles were 1 stage 1 or 2 and 9 stage 3 or 4. The average HRCTV volume was 42.1cc, 35.7cc and 51.6cc for CT, MR and MR with needles. All doses are quoted as EQD2 dose delivered over 3 fractions for CT planned, MR planned and MR with needles respectively. Average HRCTV D90 was 19.9Gy, 35Gy and 30.5Gy. Average rectal D2cc was 20.0Gy, 21.4Gy and 25.7Gy. Average bladder D2cc was 41.7Gy, 34.0Gy, and 34.7Gy (table 1) . system. Results EP-1529 Dosimetric parameters in anatomical sites correlate with blood values in cervical cancer patients Abstract withdrawn