ESTRO 2025 - Abstract Book

S1737

Clinical – Upper GI

ESTRO 2025

28

Digital Poster KRAS status as an independent prognostic factor for survival after SBRT Colorectal Cancer Liver Metastases Manoela Cholakova 1 , Kiril Zhelev 1 , Maria Mihaylova-Hristova 2 , Iglika Mihaylova 3 , Nikolay Conev 4 , Hristina Ivanovska 5 , Petya Kraleva 6 , Mila Petrova 6 , Ivan Donev 6 1 Radiotherapy and Radiosurgery, Heart and Brain Center of Clinical Excellence, Pleven, Bulgaria. 2 Nuclear Medicine, Oncology Hospital, Sofia, Bulgaria. 3 Radiotherapy, Oncology Hospital, Sofia, Bulgaria. 4 Medical Oncology, UMHAT St. Marina, Varna, Bulgaria. 5 Radiotherapy, Oncology Hospital, Varna, Bulgaria. 6 Medical Oncology, MHAT Nadezhda, Sofia, Bulgaria Purpose/Objective: We aim to assess the Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation status as a predictor of survival following Stereotactic body radiation therapy (SBRT) for colorectal cancer (CRC) liver metastases. Material/Methods: We investigated consecutive patients with unresectable CRC liver metastases and documented KRAS mutation status who underwent SBRT treatment between 2022 and 2024. We compared patient demographics, disease characteristics, therapy regimens, local control (LC), progression-free survival (PFS), and overall survival (OS) from SBRT between patients with KRAS wild-type (WT) and mutant status. We used Kaplan-Meier estimation and Cox regression for survival analysis and to assess independent prognostic factors for LC, PFS, and OS. Results: A total of 82 patients were men, 42 (51.2%) and women, 40 (48.8%), with a median age of 65±9.6. Patients with Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0 were 29 (35.4%) and PS 1–53 (64.6%). KRAS WT was found in 41 (50.0%) patients, of which 29 (35.4%) were men and 12 (14.6%) were women. KRAS WT was only related to gender (p<0.001), ECOG PS (p=0.003), and Child-Pugh (p=0.002). KRAS mutant patients had a significantly shorter mean PFS and OS than KRAS WT patients (13.43 months, 95% CI: 11.43–15.43 vs. 26.08 months, 95% CI: 23.30–28.87; p<0.001) and (21.11 months, 95% CI: 19.29–22.93 vs. 32.26 months, 95% CI: 29.66–34.87; p = 0.008). KRAS mutant patients had a significantly shorter mean local control than KRAS WT patients (15.73 months, 95% CI: 13.61–17.85 vs. 21.21 months, 95% CI: 18.48–23.93; p = 0.016). Univariate analysis identified ECOG, KRAS status, Child-Pugh class, and chemotherapy after SBRT as prognostic factors for PFS. Multivariate Cox regression analysis demonstrated that Child-Pugh class and KRAS status were independent prognostic factors for PFS, even when accounting for the effect of chemotherapy after SBRT. Univariate analysis identified KRAS status and Child-Pugh class as prognostic factors for OS. The multivariate Cox regression analysis revealed that only KRAS status was an independent prognostic factor for OS. Conclusion: Patients with CRC liver metastases and KRAS WT may derive greater survival benefits from SBRT than patients with KRAS mutants.

Keywords: KRAS, Liver Metastases, SBRT