title: A varying-coefficient cox model for the effect of CA19-9 kinetics on overall survival in patients with advanced pancreatic cancer.
abstract: OBJECTIVE
  To evaluate the relationship between serum CA19-9 and overall survival in patients with advanced pancreatic cancer.
  
  
  METHODS
  109 advanced pancreatic cancer patients with gemcitabine based first-line chemotherapy were included. The effect of pretreatment CA19-9 level on overall survival was modeled by Cox proportional hazard regression. The effect of CA19-9 kinetics on overall survival was modeled by an extended Cox regression with a time varying coefficient and a time varying covariate.
  
  
  RESULTS
  Univariate analysis indicated that baseline CA19-9 correlated with OS (HR = 1.66, p < 0.01) and this association remained significant within multivariate analysis (HR = 1.56, P < 0.01). For the analysis of CA19-9 kinetics, the extended Cox model showed that the effect of CA19-9 on overall survival changed with time: increased in the first two months and reached the top at a HR of about 2, then decreased for the next two months to a HR of about 1.56 and finally tended to be stable. The combination of pretreatment CA19-9 and CA19-9 at 2 month may better evaluate the patients' prognosis compared to pretreatment CA19-9 alone.
  
  
  CONCLUSIONS
  Pretreatment CA19-9 and CA19-9 kinetics may serve as a useful serum biomarker in advanced pancreatic cancer.
authors.affiliation: Department of Biostatistics, School of Public Health and Key Laboratory of Public Health Safety, Fudan University, Shanghai 200032, China.|Collaborative Innovation Center of Social Risks Governance in Health, Fudan University, Shanghai 200032, China.
authors.forename: Yuntao
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Collaborative Innovation Center of Social Risks Governance in Health, Fudan University, Shanghai 200032, China.
authors.forename: Zhenyi
authors.initials: Z
authors.lastname: Shao
authors.affiliation: Collaborative Innovation Center of Social Risks Governance in Health, Fudan University, Shanghai 200032, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Chen
authors.affiliation: Collaborative Innovation Center of Social Risks Governance in Health, Fudan University, Shanghai 200032, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Xie
authors.affiliation: Department of Biostatistics, School of Public Health and Key Laboratory of Public Health Safety, Fudan University, Shanghai 200032, China.|Collaborative Innovation Center of Social Risks Governance in Health, Fudan University, Shanghai 200032, China.
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Department of Biostatistics, School of Public Health and Key Laboratory of Public Health Safety, Fudan University, Shanghai 200032, China.|Collaborative Innovation Center of Social Risks Governance in Health, Fudan University, Shanghai 200032, China.
authors.forename: Guoyou
authors.initials: G
authors.lastname: Qin
authors.affiliation: Department of Biostatistics, School of Public Health and Key Laboratory of Public Health Safety, Fudan University, Shanghai 200032, China.|Collaborative Innovation Center of Social Risks Governance in Health, Fudan University, Shanghai 200032, China.
authors.forename: Naiqing
authors.initials: N
authors.lastname: Zhao
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D014408:Biomarkers, Tumor; D018395:CA-19-9 Antigen / Q000097:blood*; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging; D010190:Pancreatic Neoplasms / Q000097:blood* / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D011379:Prognosis; D016016:Proportional Hazards Models
chemical_list: D014408:Biomarkers, Tumor; D018395:CA-19-9 Antigen
keywords: CA19-9; biomarker; pancreatic cancer; prognosis; varying coefficient model