P1-012Primary tumor location and benefit of anti-EGFRs as second or later line treatment in RAS-RAS wild type mCRC patients

Abstract Background Retrospective analysis of randomized control trials suggested that right-sided tumors derive less benefit from addition of anti-epidermal growth factor receptor antibodies(anti-EGFRs) to chemotherapy as first-line therapy . Furthermore, other retrospective studies suggest that anti-EGFRs as second or later line treatment also derive less benefit in right-sided tumors compared with left-sided tumors, although there is no definitive Conclusion. Patients and Methods Patients with KRAS and RAS wild type mCRC who were treated with anti-EGFRs as second or later line treatment from 2008 to 2018 at Kameda Medical Center were included in the study. We retrospectively analyzed the difference in efficacy of anti-EGFRs according to the location of primary tumor. Results Among 69 of patients, 49 and 20 had right- and left-sided tumors, respectively. Thirty-six patients treated with chemotherapy plus anti-EGFRs (treatment A), 33 patients treated with anti-EGFRs alone (treatment B). Median overall survival was 33 month in left-sided tumors versus 22 month in right-sided tumors. Overall response rate(ORR), disease control rate(DCR), and median progression free survival(PFS) were 22%, 29% and 4.0 months in left-sided tumor and 0%, 10% and 2.5 months in right-sided tumors, respectively.(p = 0.017) Overall response rate(ORR), disease control rate(DCR), the and median progression free survival(PFS) were 9%, 40% and 4.0 months in left-sided tumor and 0%, 9% and 1 months in right-sided tumors, respectively.(p = 0.017) Conclusion Compared with left-sided tumors, right-sided tumors responded less to anti-EGFRs and had poor prognosis.