title: Right-sided colon cancer and left-sided colorectal cancers respond differently to cetuximab.
abstract: BACKGROUND
  Right-sided colon cancer (RSCC) and left-sided colorectal cancer (LSCRC) differ with respect to their biology and genomic patterns. This study aimed to examine whether the primary tumor location is associated with the response to cetuximab in patients with metastatic colorectal cancer (mCRC).
  
  
  METHODS
  Patients with mCRC treated with cetuximab and standard chemotherapy as first- or second-line treatments were compared with randomly chosen patients who were treated with chemotherapy alone between 2005 and 2013. The main outcome measures were the overall response rate (ORR), progression-free survival (PFS), and overall survival (OS). The differences in the outcome were analyzed by using the chi-squared test, Student's t test, and Kaplan-Meier method.
  
  
  RESULTS
  The treatment results of 206 patients with mCRC treated with cetuximab and standard chemotherapy as first- or second-line treatments were compared with those of 210 patients who were treated with chemotherapy alone. As a first-line treatment, cetuximab with chemotherapy was associated with a significantly higher ORR (49.4 % vs. 28.6 %, P = 0.005) as well as longer PFS (9.1 vs. 6.2 months, P = 0.002) and OS (28.9 vs. 20.1 months, P = 0.036) than chemotherapy alone in patients with LSCRC. However, cetuximab neither improved the ORR (36.4 % vs. 26.2 %, P = 0.349) nor prolonged PFS (5.6 vs. 5.7 months, P = 0.904) or OS (25.1 vs. 19.8 months, P = 0.553) in patients with RSCC. As a second-line treatment, cetuximab exhibited a tendency to improve the ORR (23.5 % vs. 10.2 %, P = 0.087) and prolong PFS (4.9 vs. 3.5 months, P = 0.064), and it significantly prolonged OS (17.1 vs. 12.4 months, P = 0.047) compared with chemotherapy alone in the patients with LSCRC. In contrast, as a second-line treatment, cetuximab neither improved the ORR (7.1 % vs. 11.4 %, P = 0.698) nor prolonged PFS (3.3 vs. 4.2 months, P = 0.761) or OS (13.4 vs. 13.0 months, P = 0.652) in patients with RSCC.
  
  
  CONCLUSIONS
  The addition of cetuximab to chemotherapy in both first- and second-line treatments of mCRC may only benefit patients with primary LSCRC.
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. wangfeng@sysucc.org.cn.
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. bailong@sysucc.org.cn.
authors.forename: Long
authors.initials: L
authors.lastname: Bai
authors.affiliation: Department of Medical Oncology, Zhongshan Hospital, Fudan University, Shanghai, 200032, P. R. China. liu.tianshu@zs-hospital.sh.cn.
authors.forename: Tian-Shu
authors.initials: TS
authors.lastname: Liu
authors.affiliation: Department of Medical Oncology, Zhongshan Hospital, Fudan University, Shanghai, 200032, P. R. China. yu.yiyi@zs-hospital.sh.cn.
authors.forename: Yi-Yi
authors.initials: YY
authors.lastname: Yu
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. hemm@sysucc.org.cn.
authors.forename: Ming-Ming
authors.initials: MM
authors.lastname: He
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. liuky@sysucc.org.cn.
authors.forename: Kai-Yan
authors.initials: KY
authors.lastname: Liu
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. luohy@sysucc.org.cn.
authors.forename: Hui-Yan
authors.initials: HY
authors.lastname: Luo
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. zhangdsh@sysucc.org.cn.
authors.forename: Dong-Sheng
authors.initials: DS
authors.lastname: Zhang
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. jinying1@sysucc.org.cn.
authors.forename: Yin
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. wangfh@sysucc.org.cn.
authors.forename: Feng-Hua
authors.initials: FH
authors.lastname: Wang
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. wangzhq@sysucc.org.cn.
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Wang
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. wangdsh@sysucc.org.cn.
authors.forename: De-Shen
authors.initials: DS
authors.lastname: Wang
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. qiumzh@sysucc.org.cn.
authors.forename: Miao-Zhen
authors.initials: MZ
authors.lastname: Qiu
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. renchao@sysucc.org.cn.
authors.forename: Chao
authors.initials: C
authors.lastname: Ren
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. liyh@sysucc.org.cn.
authors.forename: Yu-Hong
authors.initials: YH
authors.lastname: Li
authors.affiliation: Department of Medical Oncology, Sun Yat-sen University Cancer Center: State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, P. R. China. xurh@sysucc.org.cn.
authors.forename: Rui-Hua
authors.initials: RH
authors.lastname: Xu
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols; D000068818:Cetuximab; D003110:Colonic Neoplasms; D015179:Colorectal Neoplasms; D018572:Disease-Free Survival; D006801:Humans; D012189:Retrospective Studies
chemical_list: D000068818:Cetuximab