title: Characteristics of Differently Located Colorectal Cancers Support Proximal and Distal Classification: A Population-Based Study of 57,847 Patients.
abstract: BACKGROUND
  It has been suggested that colorectal cancer be regarded as several subgroups defined according to tumor location rather than as a single entity. The current study aimed to identify the most useful method for grouping colorectal cancer by tumor location according to both baseline and survival characteristics.
  
  
  METHODS
  Cases of pathologically confirmed colorectal adenocarcinoma diagnosed from 2000 to 2012 were identified from the Surveillance, Epidemiology, and End Results database and categorized into three groups: right colon cancer (RCC), left colon cancer (LCC), and rectal cancer (ReC). Adjusted hazard ratios for known predictors of disease-specific survival (DSS) in colorectal cancer were obtained using a Cox proportional hazards regression model.
  
  
  RESULTS
  The study included 57847 patients: 43.5% with RCC, 37.7% with LCC, and 18.8% with ReC. Compared with LCC and ReC, RCC was more likely to affect old patients and women, and to be at advanced stage, poorly differentiated or un-differentiated, and mucinous. Patients with LCC or ReC had better DSS than those with RCC in subgroups including stage III or IV disease, age ≤70 years and non-mucinous adenocarcinoma. Conversely, patients with LCC or ReC had worse DSS than those with RCC in subgroups including age ˃70 years and mucinous adenocarcinoma.
  
  
  CONCLUSIONS
  RCC differed from both LCC and ReC in several clinicopathologic characteristics and in DSS. It seems reasonable to group colorectal cancer into right-sided (i.e., proximal) and left-sided (i.e., distal) ones.
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Jiao
authors.initials: J
authors.lastname: Yang
authors.affiliation: Department of Epidemiology, Human Genetics, and Environmental Sciences, The University of Texas School of Public Health, Houston, TX, United States of America.
authors.forename: Xiang Lin
authors.initials: XL
authors.lastname: Du
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Shu Ting
authors.initials: ST
authors.lastname: Li
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Bi Yuan
authors.initials: BY
authors.lastname: Wang
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Yin Ying
authors.initials: YY
authors.lastname: Wu
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Zhe Ling
authors.initials: ZL
authors.lastname: Chen
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Lv
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Yan Wei
authors.initials: YW
authors.lastname: Shen
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Dan Feng
authors.initials: DF
authors.lastname: Dong
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Wang
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: En Xiao
authors.initials: EX
authors.lastname: Li
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.|Department of Breast Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States of America.
authors.forename: Min
authors.initials: M
authors.lastname: Yi
authors.affiliation: Department of Medical Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an city, Shaanxi Province, China.
authors.forename: Jin
authors.identifier: http://orcid.org/0000-0001-7754-7723
authors.initials: J
authors.lastname: Yang
mesh_terms: D000230:Adenocarcinoma / Q000145:classification / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003110:Colonic Neoplasms / Q000473:pathology; D015179:Colorectal Neoplasms / Q000145:classification / Q000473:pathology*; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D016016:Proportional Hazards Models; D012004:Rectal Neoplasms / Q000473:pathology; D018426:SEER Program / Q000706:statistics & numerical data; D014481:United States; D055815:Young Adult