ESTRO 2023 - Abstract Book

S720

Monday 15 May 2023

ESTRO 2023

partial response to chemoradiotherapy had detectable ctDNA at the end of treatment but attained molecular remission when adjuvant durvalumab was initiated (see lower figure). Conclusion Serial ctDNA analysis may provide clinical useful information. A “spike” in ctDNA was detected after the first fraction in 4 of 5 patients treated with fractionated radiotherapy. This phenomenon, which may represent rapid initial tumour cell destruction, could have clinical value as a surrogate for early treatment response and as a means of enriching plasma for ctDNA for mutational profiling.

MO-0874 Nutritional and inflammatory status as biomarkers in oligorecurrent PCa (RADIOSA TRIAL): an update M. Zaffaroni 1 , G. Marvaso 1,8 , G. Corrao 1 , M.G. Vincini 1 , F. Cattani 2 , F.A. Mistretta 3 , S. Luzzago 3 , G. Musi 3,8 , S. Alessi 4 , C. Fodor 1 , G. Petralia 5 , G. Pravettoni 6,8 , O. De Cobelli 3,8 , R. Orecchia 7 , B.A. Jereczek-Fossa 1,8 1 IEO, European Institute of Oncology IRCCS, Division of Radiation Oncology, Milan, Italy; 2 IEO, European Institute of Oncology IRCCS, Unit of Medical Physics, Milan, Italy; 3 IEO, European Institute of Oncology IRCCS, Department of Urology, Milan, Italy; 4 IEO, European Institute of Oncology IRCCS, Division of Radiology, Milan, Italy; 5 IEO, European Institute of Oncology IRCCS, Precision Imaging and Research Unit, Milan, Italy; 6 IEO, European Institute of Oncology IRCCS, Applied Research Division for Cognitive and Psychological Science, Milan, Italy; 7 IEO, European Institute of Oncology IRCCS, Scientific Directorate, Milan, Italy; 8 University of Milan, Department of Oncology and Hemato-Oncology, Milan, Italy Purpose or Objective SBRT represents a low-toxicity treatment for prostate cancer localizations that may allow delaying the start of androgen deprivation therapy (ADT) in the oligometastatic setting. In the RADIOSA phase II randomized trial (NCT03940235), the biology task entails the identification of predictive and prognostic biomarkers in the context of oligorecurrent, castration sensitive PCa in order to distinguish polymetastatic from oligometastatic disease. This may lay the groundwork for personalized treatments for those patients who could really benefit from metastases-directed therapies. Materials and Methods According to the administration of ADT and the location of the metastases, patients who matched the inclusion criteria were divided into two treatment groups: SBRT only on all lesions (arm A) vs SBRT on all lesions + 6 months ADT (arm B). Common serum-derived biomarkers were collected at baseline and at 3 months after RT. The prognostic nutritional index, an immune and nutrition-based prognostic score, and the controlling nutritional status (CONUT) score, a scoring system for evaluating patient’s nutritional status, were calculated in accordance with the body of available literature. As inflammatory indicators, neutrophil-lymphocyte ratio (NLR) and the NLR-albumin ratio (NLRAR) were assessed. Changes in these parameters between baseline and the 3-months timepoint were evaluated both in absolute and relative values. Significant