ESTRO 2023 - Abstract Book

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ESTRO 2023

50%, and 60% of the SUVmax) extracted from pre-treatment 18F-FDG-PET/CT were analyzed for all lesions.

One month after last chemotherapy course, treatment response was evaluated by PERCIST 1.0, and patients were categorized in 4 class types: complete metabolic response (CMR), partial metabolic response (PMR), progressive metabolic disease (PMD), and stable metabolic disease (SMD). Data analyses performed using Wilcoxson statistical method, thresholding by the interquartile range, and Classification and Regression Tree algorithm (CART). SPSS software (IBM, v. 26) and SPSS modelar (IBM, v.18) was used. Results A total of 303 lesions were examined. Evaluation at median point of follow up (8.3 month) represented 188, 22 ,46 and 47 lesions for CMD, PMR, SMD, and PMD categories respectively. By applying knowledge expert in the model, Table 1 presents the rules and related accuracy for each category;

Important prognosis factors included Age, Gender, B symptoms, ECOG scale, pathologic subtype, tumor stage, previous radiotherapy, SUVMAXL, TLG50, TLG60 and SUVPL and SUVPM. Conclusion This preliminary study found that clinical and image-based measures extracted from pre-treatment 18F-FDG PET/CT imaging might be helpful in identifying important prognostic features related to salvage therapy response in the relapsed/refractory HL.

PO-2122 Effect of early fractional lymphocyte loss on lymphopenia probability models for NSCLC

T. Kanehira 1 , H. Taguchi 2 , N. Katoh 3 , Y. Uchinami 4 , T. Yoshimura 5 , M. Tamura 1 , R. Suzuki 1 , T. Hashimoto 6 , H. Aoyama 4

1 Hokkaido University Hospital, Department of Medical Physics, Sapporo, Japan; 2 Hokkaido University Hospital, Department of Radiation Oncology, Sapporo, Japan; 3 Hokkaido University, Department of Radiation Oncology, Faculty of Medicine and Graduate School of Medicine, Sapporo, Japan; 4 Hokkaido University, Department of Radiation Oncology, Faculty of Medicine and Graduate School of Medicine, Sapporo, Japan; 5 Hokkaido University, Department of Health Sciences and Technology, Faculty of Health Sciences, Sapporo, Japan; 6 Hokkaido University, Department of Radiation Medical Science and Engineering, Faculty of Medicine, Sapporo, Japan Purpose or Objective Radiotherapy (RT) for NSCLC causes radiation-induced lymphopenia (RIL) possibly affecting survival. In a recent study, fractional lymphocyte loss (FLL) observed in early radiation fractions was related to overall reduction in absolute lymphocyte count (ALC) for several tumor sites, which can be used to predict RIL. For a lung region, however, FLL and its effect on RIL prediction are unknown. This study aimed to evaluate whether FLL improves RIL probability model for NSCLC patients. Materials and Methods We included 84 stage Ⅰ - Ⅲ NSCLC patients who received concurrent chemo-radiotherapy between 2011 and 2022 in our hospital. Prescribed dose of 60 Gy in 30 fractions (Fx) or 66 Gy in 33 Fx to planning target volume was delivered with either/both 3D-CRT or/and IMRT. ALCs were collected from blood tests from 1 week before RT start till 1 week after RT