ESTRO 36 Abstract Book

S165 ESTRO 36 _______________________________________________________________________________________________

Gambacorta 1 , R. Autorino 1 , M. Campitelli 1 , A. Testa 3 , G. Chiloiro 1 , J. Lenkowicz 1 , C. Casà 1 , G. Scambia 3 , L. Bonomo 2 , V. Valentini 1 1 Università Cattolica del Sacro Cuore -Policlinico A. Gemelli, Radiation Oncology Department , Rome, Italy 2 Università Cattolica del Sacro Cuore -Policlinico A. Gemelli, Radiology Department, Rome, Italy 3 Università Cattolica del Sacro Cuore -Policlinico A. Gemelli, Gynecology Department, Rome, Italy Purpose or Objective Standard treatment in cervical cancer (CC) is largely based on chemoradiation (CRT) for locally advanced stages. The role of surgery after a first time of CRT is limited to selected protocols. In such cases it is possible to assess the pathological complete response (PCR). A fractal is an object having geometric shape that can be divided into subparts, each of which is a reduced copy of the whole. This property, known as self-similarity, can be measured by the Fractal Dimension (FD). Aim of this study is finding an enhanced by FD radiomics signature detecting patients with PCR. Material and Methods Pathologically proven CC patients underwent to CRT after MR definition of the local stage. T2 High-Resolution images were used for delineating GTV. A home-made software was used for assessing radiomics features after pre- processing images by Laplacian of Gaussian (LoG) filter and tuning its σ parameter, and for extracting fractal dimension (FD) on raw images. FD was extracted at different threshold levels considering all deciles between 10% and 100% of signal intervals inside the GTV volume analyzed slice by slice by using the box-counting technique. Stepwise logistic regression (SLR) models were used for predicting PCR using FIGO Stage, 1 st order features (skewness, kurtosis, entropy) and different thresholds for FD. AUC of ROC and calibration, were determined for internal validation. Results 177 patients were retrospectively recruited (FIGO stage Ib – IVb). FD was the only significant predictor for the whole dataset in SLR (MaxDF@10%: P-Value<0.001, MinDF@0- 90%: P-Value<0.05, see fig. 1). AUC of ROC was 0.70 with not significant deviance at calibration. After selecting patients according to the MR pixel spacing (PS) the most numerous group was found in patients having PS=0.58mm (69 patients). A new SLR model showed significance of entropy (σ=2.36mm, P-Value<0.05), kurtosis (σ=1.23mm, P-Value<0.01) and MinDF@0-90% (P-Value<0.01), with AUC

of ROC=0.80 and not significant deviance in calibration.

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,