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Analysis of Therapeutic Effects of Cetuximab and Bevacizumab Related to the Primary Tumor Site in Patients with Metastatic Colorectal Cancer
J. Kor. Soc. Health-syst. Pharm. 2021;38:6-17
Published online February 28, 2021;
© 2021 Korean Society of Health-System Pharmacists

Yoo Jin Kim, Hye Lim Ahn, Eyn Young Kwon

Department of Pharmacy, Seoul St. Mary’s Hospital, The Catholic University of Korea 222 Banpo-daero, Seocho-gu, Seoul, 06591, Republic of Korea
Correspondence to: †교신저자 김유진 Tel:02-2258-2562
Received August 17, 2020; Revised October 19, 2020; Accepted December 16, 2020.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background : Recent reports on metastatic colorectal cancer (mCRC) demonstrated that the primary tumor origin site was related to significantly different effects of biologic therapy (BT). However, in the Korean clinical field, patients are still prescribed cetuximab regardless of the primary tumor site. Therefore, it is necessary to determine whether there is a different response to BT in Korean patients as well. This study analyzed the correlation between the effect of BT and the primary tumor origin in patients with mCRC.
Methods : This study included all patients diagnosed with mCRC from January 1, 2015, through December 31, 2016, who were treated with first-line chemotherapy containing bevacizumab or cetuximab. We followed the patients using EMR analysis until September 30, 2018. We compared the different effects of BT based on the primary tumor site by the time to progression (TTP) and the overall response rate (ORR).
Results : One hundred and sixty-one patients were eligible for the study, 50 patients had right-sided primary tumor origins and 111 patients had tumors on the left. Among patients who received bevacizumab, there was no significant difference regardless of the primary tumor site, whereas, in patients treated with cetuximab, left-sided mCRC was related to longer TTP compared to right-sided (hazard ratio [HR]=1.92, 95% CI: 0.98 – 3.60; p=0.050). In other words, there was no significant difference between bevacizumab and cetuximab in the left-sided mCRC patients. However, in the right-sided mCRC patients, bevacizumab showed a significantly improved TTP compared to cetuximab (HR=2.08, 95% CI: 1.03 – 4.03; p=0.036).
Conclusion : The primary tumor site was related to the response to BT in patients with mCRC. Right-sided primary tumor origin was associated with significantly improved TTP when treated with bevacizumab compared to cetuximab. Therefore, we recommend considering not only the molecular status but the primary tumor site when choosing BT for mCRC patients in the future.
Keywords : Metastatic colorectal cancer, Right/left side primary tumor, Bevacizumab, Cetuximab, TTP, ORR

February 2021, 38 (1)