ESTRO 36 Abstract Book

S164 ESTRO 36 2017 _______________________________________________________________________________________________

of ROC=0.80 and not significant deviance in calibration.

V30, and V40) were obtained. Receiver operating characteristic (ROC) curve identified DVH thresholds that predicted for grade≥ II HT toxicity with highest specificity. All data was dichotomized across these cut-offs. Univariate and multivariate analysis was performed with SPSS, version 20. Results Of the 94 patients randomized to IMRT arm, 74 received concurrent cisplatin (median cycles=4). Grades I-V HT was seen in 55.5%, 32.5%, 5%, 0% and 0% patients, respectively demonstrating low incidence of HT during bowel sparing IMRT. Leukopenia, neutropenia, anemia, and thrombocytopenia ≥ grade II was observed in 24.3%, 5.3%, 17.6%, and 0%, respectively. None of the HT resulted in treatment break. On comparing BM delineation techniques the FH sub volumes were 25%-47% of WB sub-volumes. The mean V 5 , V10, V20, V30, and V40 for WP FH and WB were 99%, 93%, 77%, 60%, and 36%; and 99%, 94%, 80%, 60%, and 36%, respectively suggesting unintended desirable BM sparing. On univariate analysis WPL FH V30 > 55% (p=0.04) predicted for overall grade ≥ II HT, WP V10 >95% (p= 0.04) for grade ≥ II leucopenia and ilium V20 > 90% (p=0.04) for hemoglobin toxicity. On multivariate analysis, only WP FH V10 >95% (p value 0.04, OR 3.3 (1-11.5) was statistically significant for grade ≥ II leucopenia. Conclusion The IMRT arm of NCT01279135 (PARCER study) that employed strict bowel constraints also had unintentional dosimetrically desirable BM sparing. This was associated with low absolute rates of HT. Within the setting of bowel sparing IMRT WP FH V10 should be restricted to ≤95% for simultaneous bowel and BM sparing. However as none of the other dosimetric variables predicted for HT, WB marrow contours could serve as a resource sparing strategy while planning pelvic IMRT. OC-0319 Cervix cancer: dose-volume effects in pathologic lymph nodes W. Bacorro 1 , R. Mazeron 2 , I. Dumas 3 , A. Escande 2 , A. Huertas 2 , R. Sun 2 , P. Castelnau-Marchand 2 , C. Haie- Meder 2 , C. Chargari 2 1 Benavides Cancer Institute- UST Hospital, Radiation Oncology, Manila, Philippines 2 Gustave Roussy, Radiation Oncology, Villejuif, France 3 Gustave Roussy, Medical Physics, Villejuif, France Purpose or Objective Whereas clear dose-volume relationships have been demonstrated for the tumor and organs at risk in locally advanced cervix cancer, the optimal threshold to reach for pathologic lymph nodes remains uncertain. The objective was to identify planning aim for pathologic nodes. Material and Methods Patients treated with curative intent for a cervical cancer with nodal involvement were identified. Their treatment combined external beam radiotherapy (EBRT) and image- guided brachytherapy (IGABT). Nodal boosts were performed sequentially or using the simultaneous integrated boost (SIB) technique depending on the EBRT technique used. The contributions of EBRT, IGABT (D 98 ) and nodal boosts were converted in 2-Gy equivalent (α/β=10 Gy) and summed. Each node was considered individually, and followed from diagnosis to relapse. Resected nodes during para-aortic node surgical staging were not considered. Statistical analyses comprised log- rank tests (univariate analyses), Cox proportional model (factors with p ≤0.1 in univariate) and probit analyses. Results One hundred and fifteen patients were included, with a total number of nodes of 288 (2.5 per patient). PET-CT was performed in 90.6% of the patients; para-aortic dissection in 53.8%. Histologic subtypes comprised squamous cell carcinomas (SCC) in 88.9%, adenocarcinomas in 8.5% and adenosquamous in 2.6%. The

Conclusion Radiomics can be an interesting perspective for detecting patients with CC who will show PCR and subsequently could result in better prognosis. Even considering that CRT followed by surgery is not a standard treatment this workflow gave us the chance to analyze the relationship between radiomics signature and pathological findings, not feasible in CRT alone. An external validation of the signature is planned to evaluate the stability of this model by using different MR scanners at diagnosis time. OC-0318 Hematological toxicity during bowel sparing IMRT: Exploratory analysis from PARCER Phase III trial. S. Lewis 1 , S. Chopra 1 , P. Naga 1 , N. Bharadwaj 1 , E. Dandpani 1 , U. Mahantshetty 1 , R. Engineer 1 , J. Swamidas 1 , J. Ghosh 2 , S. Gupta 2 , S. Shrivastava 1 1 Tata memorial centre, radiation oncology, Mumbai,India 2 Tata memorial centre, medical oncology, Mumbai,India Purpose or Objective To report acute hematological toxicity (HT) and dose volume correlates in patients receiving postoperative bowel sparing intensity-modulated radiotherapy (IMRT) and cisplatin within a Phase III trial for late bowel toxicity reduction in patients with cervical cancer. Material and Methods Clinical database of Phase III trial (NCT01279135) that randomizes patients to IMRT (Tomotherapy) and 3DCRT was searched to select patient strata that received IMRT (50 Gy/25#/5 wks) and concurrent cisplatin (40 mg/m 2 ) from Jan, 2011 to Jun, 2016. The IMRT planning aimed at restricting V15 and V40 Small Bowel to ≤ 200 and 100 cc respectively. No prospective bone marrow (BM) constraints were applied. The data base was reviewed to determine worst grade of HT toxicity. IMRT planning scans were dearchived and pelvic BM was delineated in 2 sets; whole bone (WB), and freehand (FH) inner cavity of bone from top of L3 vertebra to ischial tuberosity. Various BM sub-volumes namely whole pelvis + lumbar (WPL), lumbar vertebra, sacrum, ilium, ischium, femoral head and neck, whole pelvis (WP), lower pelvis(LP) were contoured and dose volume histograms (DVH) parameters (V 5 , V10, V20,