ESTRO 2022 - Abstract Book

S218

Abstract book

ESTRO 2022

The C-index of the model was 0.71 (95% CI: 0.69-0.72). The slope and intercept of calibration curve were 0.97 and 0.011, respectively. The observed versus predicted 5-year DFS was 84% vs. 83% in the control arm and 91% vs. 92% in the focal boost arm. The distribution of predicted outcomes for all patients given the actual D98% they received in the trial is shown in Figure 1. On the right side are the predictions if all would have received 77 Gy (bottom), or if all would have had a boost dose of 95 Gy (top). Figure 2 shows the predictions for separate categories of ISUP grade and T-stage. A trend towards a larger improvement with a focal boost was observed for patients with high ISUP grade disease. There was no trend observed for the impact of a focal boost for different clinical T-stages.

Conclusion We developed a prediction model for DFS in patients with intermediate and high-risk prostate cancer treated with radiotherapy. The model shows reasonable discrimination and good calibration. The model can be used to identify patients who most likely require focal boosting through evaluation of their predicted probability of 5-year DFS. The improvement in the predicted DFS with a boost dose of 95 Gy, compared to the DFS with the actually delivered boost dose, suggests the possible gain if alternative techniques of high focal boost delivery are applied for these patients.

OC-0260 Predictive value of inflammatory markers in LARC patients undergoing neoadjuvant chemoradiotherapy

S. Mariani 1 , V. Chiloiro 2 , N.D. Capocchiano 3 , M. Savino 4 , S. Reina 4 , E. Meldolesi 5 , C. Coco 6 , B. Corvari 5 , A. Damiani 3 , V. De Luca 5 , S. Manfrida 5 , R. Persiani 7 , S. Alfieri 8 , V. Valentini 5 , M.A. Gambacorta 5 1 Università Cattolica del Sacro Cuore, UOC di Radioterapia Oncologica, Dipartimento Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy; 2 Radioterapia Oncologica, Dipartimento Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy; 3 Radioterapia Oncologica, Gemelli Generator, Fondazione Policlinico Agostino Gemelli IRCCS, Rome, Italy; 4 Radioterapia Oncologica, Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Fondazione Policlinico A. Gemelli IRCCS - Università Cattolica Sacro Cuore, Rome, Italy; 5 Radioterapia Oncologica, Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Fondazione Policlinico Universitario 'Agostino Gemelli' IRCCS, Rome, Italy; 6 Chirurgia generale, Chirurgia generale, Fondazione Policlinico Universitario 'Agostino Gemelli' IRCCS, Rome, Italy; 7 Chirurgia Generale, Scienze mediche e chirurgiche, Fondazione Policlinico Universitario 'Agostino Gemelli' IRCCS, Rome, Italy; 8 Chirurgia Generale, Chirurgia digestiva, Fondazione Policlinico Universitario 'Agostino Gemelli' IRCCS, Rome, Italy Purpose or Objective Patients (pts) affected by locally advanced rectal cancer (LARC) may respond differently to neoadjuvant chemoradiotherapy (nCRT). The identification of reliable biomarkers for oncologic outcomes could help in the development of risk-adapted treatment strategies. There is evidence of a role of inflammation parameters as prognostic factors for survival outcomes in different cancer types. Hemo-eosinophils inflammation (HEI) index, comprising systemic inflammation index (SII), hemoglobin (Hb) and eosinophils levels, was recently highlighted as a predictor of disease-free survival (DFS) and overall survival (OS) in anal cancer pts treated with CRT. The aim of the present study is to evaluate baseline inflammatory markers as prognostic factors in a large cohort of LARC pts. Materials and Methods Pts undergoing nCRT for LARC from January 2010 to December 2019 were retrospectively analyzed. Pts underwent long- course RT with chemotherapy based on fluoropyrimidine ± oxaliplatin. Surgery was performed after re-evaluation at least 8 weeks after the end of CRT. Adjuvant chemotherapy was an option, depending on risk factors. Pts with a follow-up time of less than 2 years were excluded. We collected data related to clinical and laboratory parameters, disease stage, treatments characteristics, pathological staging and patients’ status. Pre-treatment blood samples were taken and inflammatory markers were calculated including HEI, SII, NLR (neutrophil/lymphocyte ratio), PLR (platelet/lymphocyte ratio) and MLR (monocyte/lymphocyte ratio). The inflammatory marker values were discretized into a variable number of