ESTRO 2024 - Abstract Book

S2433

Clinical - Urology

ESTRO 2024

1409

Digital Poster

Liquid biopsy-based molecular characterization of oligometastatic state: A RADIOSA trial side study

Mattia Zaffaroni 1 , Giulia Marvaso 1 , Maria Giulia Vincini 1 , Chiara Lorubbio 1 , Konstantinos Venetis 2 , Giulia Corrao 1 , Federica Cattani 3 , Francesco Alessandro Mistretta 4 , Stefano Luzzago 4 , Gennaro Musi 4 , Cristiana Fodor 1 , Giuseppina Bonizzi 5 , Sara Gandini 6 , Giuseppe Petralia 7 , Gabriella Pravettoni 8 , Ottavio De Cobelli 4 , Nicola Fusco 9 , Barbara Alicja Jereczek-Fossa 1 1 IEO European Institute of Oncology IRCCS, Milan, Italy, Division of Radiation Oncology, Milan, Italy. 2 IEO European Institute of Oncology IRCCS, Milan, Italy, Division of Radiation Pathology, Milan, Italy. 3 IEO European Institute of Oncology IRCCS, Milan, Italy, Unit of medical physics, Milan, Italy. 4 IEO European Institute of Oncology IRCCS, Milan, Italy, Division of Urology, Milan, Italy. 5 IEO European Institute of Oncology IRCCS, Milan, Italy, Biobank for Translational and Digital Medicine, Milan, Italy. 6 IEO European Institute of Oncology IRCCS, Milan, Italy, Department of Experimental Oncology, Milan, Italy. 7 IEO European Institute of Oncology IRCCS, Milan, Italy, Division of Radiology, Milan, Italy. 8 IEO European Institute of Oncology IRCCS, Milan, Italy, Applied Research Division for Cognitive and Psychological Science,, Milan, Italy. 9 IEO European Institute of Oncology IRCCS, Milan, Italy, Division of Pathology, Milan, Italy

Purpose/Objective:

The biological task of phase II randomized trial RADIOSA (NCT03940235) aims to identify predictive and prognostic biomarkers in the context of hormone sensitive oligoreccurent prostate cancer (PCa). The objective of the present study is to define whether a liquid biopsy-based high-risk mutational signature exist in this setting of patients able to strongly correlate with the oncological outcomes of interest and to distinguish the true oligometastatic patients from those who are going to develop a polymetastatic progression.

Material/Methods:

Oligorecurrent PCa pts with 3 or less bone or lymph nodal localizations where randomized 1:1 to receive SBRT alone (arm A) or SBRT + 6 months of ADT (arm B). For molecular biology analyses 10ml of blood were collected at one of the three timepoints indicated in the protocol, specifically: (i) time of randomization, (ii) follow-up visits and (iii) the eventual clinical progression ( Figure 1 ). Blood was collected in Roche Cell-Free DNA Collection Tubes® (Roche, Switzerland) and processed within 24 h. Plasma was separated by centrifugation at 2,000 × g for 10 min at 4°C. Next, to further purify plasma from corpuscular cells, the supernatant is centrifuged at 20,000 × g for 10 min at 4°C. finally, the processed plasma will be stored at −80°C until analysis. ctDNA will be extracted from 2 ml of plasma using the Maxwell® RSC ccfDNA Plasma Kit, according to manufacturer instructions (Promega, Madison, Wisconsin, USA). Analyses will be carried out using the KAPA HyperPETE Pan Cancer Panel that targets 1321 target regions, 86 cancer related genes and 190 MSI loci. Library amplification will be carried manually according to manufacturer instructions. A total of 10-50 ng will be used following standardized thermal conditions. Libraries will be loaded on a NextSeq 550 (Illumina, San Diego, California, USA) following manufacturer instructions. Only single nucleotide variants with a minimum coverage depth of 500×, allele coverage and a quality score ≥ 20, and a minimum variant frequency of 1% will be reported.