ESTRO 2021 Abstract Book

S307

ESTRO 2021

Medical Center, Surgery, Leiden, The Netherlands; 12 Surgery, Leiden University Medical Center, Leiden, The Netherlands; 13 Amsterdam University Medical Centers, Medical Oncology, Amsterdam, The Netherlands; 14 Radboud University Medical Center, Radiation Oncology, Nijmegen, The Netherlands Purpose or Objective Carcinoembryonic antigen (CEA) and carbohydrate antigen (CA) 19-9 are well-known tumor markers. Most studies on CEA and CA 19-9 in patients with gastric cancer were performed in Asia, and/or in the metastatic setting. The aim of this study was to investigate the prognostic value of blood derived laboratory parameters in a cohort of European patients with resectable non-metastatic gastric cancer treated with perioperative In the CRITICS trial, 788 patients with resectable gastric cancer were randomized between preoperative chemotherapy (3 cycles of epirubicin, cisplatin/oxaliplatin, and capecitabine (ECC/EOC)) plus postoperative chemotherapy (3 cycles of ECC/EOC) or preoperative chemotherapy (3 cycles of ECC/EOC) plus postoperative chemoradiotherapy (45 Gy in 25 fractions of 1.8 Gy plus capecitabine and cisplatin). Blood levels of CEA, CA 19-9, alkaline phosphatase, creatinine, neutrophils, hemoglobin and lactate dehydrogenase were determined prior to treatment. Data for these variables were available for at least 89% of the patients. Factors significant on univariable cox regression analysis were further explored in multivariable analysis. Probabilities to undergo potentially curative surgery was investigated for factors significant on multivariable analysis. The relationship between tumor markers and the presence of circulating tumor DNA (ctDNA) was explored in 50 patients with available ctDNA data. Results CEA and CA 19-9 were identified as independent prognostic factors for survival in multivariable analysis (Table 1). Probabilities to undergo potentially curative surgery were 86%, 77% and 60% for patients with no elevated tumor makers versus those with elevated CEA or elevated CA 19-9 versus those with both tumor markers elevated, respectively (p<0.001). No relationship was found between elevated tumor marker(s) and the presence of ctDNA neither pretreatment nor preoperatively chemo(radio)therapy. Materials and Methods

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Conclusion Pretreatment blood levels of CEA and CA 19-9 were identified as prognostic factors for overall survival in a large cohort of European gastric cancer patients with potentially curable disease. Tumor markers may guide treatment choices at an early phase but might in the future also be included in a decision tool whether or not to offer postoperative chemo(radio)therapy.

OC-0412 Quality of life associated with survival in gastric cancer patients: Results from the CRITICS trial R. van Amelsfoort 1 1 Netherlands Cancer Institute, Radiation Oncology, Amsterdam, The Netherlands Purpose or Objective The evaluation of health-related quality of life (HRQOL) in clinical trials has become increasingly important, since it addresses the impact of treatment from the patient’s perspective. In the multicenter randomized CRITICS trial no significant differences in overall survival (OS) and event-free survival (EFS) were found between postoperative chemotherapy (CT) and chemoradiotherapy (CRT) after neo-adjuvant chemotherapy and D2 gastric cancer surgery (intention-to-treat). The primary aim of this study was to investigate the potential prognostic value of pretreatment HRQOL on EFS and OS in the CRITICS trial.