ESTRO 2021 Abstract Book

S1650

ESTRO 2021

Conclusion Further investigations need to be performed towards the identification of a pattern in the tumor aggressiveness-response in PCa treated with ultra-hypofractionated radiotherapy. Moreover, a possible relationship between biomarker analysis and imaging textural features could be also explored. PO-1936 Performances of a binary blood assay for predicting radiosensitivity S. Deneuve 1 , C. Mirjolet 2 , T. Bastogne 3 , M. duclos 4 , P. Retif 5 , P. Zrounba 6 , P.E. Roux 6 , M. Poupart 6 , G. Vogin 7 , N. Foray 8 , S. Pereira 9 1 Centre Léon Bérard, Surgical oncology, Lyon, France; 2 Centre Georges François Leclerc, radiotherapy, Dijon, France; 3 institut de Cancérologie de Lorraine, CRAN CNRS UMR 7039, Vandoeuvre les Nancy, France; 4 ALARA, neolys diagnostics, strasbourg, France; 5 CHR Metz Thionville, Medical Physics Department, Metz Thionville, France; 6 Centre Léon Bérard, Surgical Oncology, Lyon, France; 7 Centre Francois baclesse, Radiotherapy, Esch-sur-Alzette, Luxembourg; 8 UA8 Inserm, Radiobiology, Lyon, France; 9 UA8, inserm, Radiobiology Group, Lyon, France Purpose or Objective Radiation therapy (RT), either alone or in combination with surgery and/or chemotherapy plays an essential role in the treatment of most cancers its side-effects are not rare, and can sometimes lead to the suspension of the treatment. Recent studies have stressed the role of the pATM protein and the discrimination power of this molecular endpoint in predicting individual radiosensitivity and a unified model based on Radio-Induced ATM Nucleoshuttling (RIANS) has been proposed. From this model, two tests developed first on skin samples have been shown to reliably predict both individual radiosensitivity and severity of radiotherapy adverse events. In order to obtain a faster and less invasive assay, that could be used in clinical practice, we here assess the reliability of a new approach. This assay, named RADIODTECT©, is based on the quantification of total pATM on blood lymphocytes to predict intrinsic patient radiosensitivity and their risk of toxicity. Materials and Methods A blind pilot retrospective study was performed on 150 blood lymphocytes of patients with different cancer types. Patients were divided into 2 groups, according to their observed side effects, classified according to the CTCAEV 4.0. Sixty-one patients with acute side effects graded <2 were considered as radioresistant (RR) and eighty-nine patients with acute side effects graded ≥2 were considered as radiosensitive (RS). The global quantity of pATM molecules was assessed by ELISA method on extracted patient lymphocytes. A classification study was carried out to estimate the threshold value of the biomarker able to minimize the number of false positive cases (RS patients inaccurately identified as RR). Results Quantities of pATM molecules in each sample were found in agreement with the observed CTCAE grades. ROC analysis was performed on pATM elisa results and a Wilcoxon rank sum test was also applied to compare RR and RS groups (p <0,001) (Figure 1). Statistical results showed the following mean values concerning the classification into RR or RS performances: sensitivity=0.85, specificity=0.54, AUC=0.71, NPV=0.53 and PPV=0.85.

Figure 1: Determination of optimized threshold and prediction results of the 150 patients