title: Survival of Colorectal Cancer in the Presence of Competing- Risks - Modeling by Weibull Distribution.
abstract: BACKGROUND
  Colorectal cancer (CRC) is the commonest malignancy in the lower gastrointestinal tract in both men and women. It is the third leading cause of cancer-dependent death in the world. In Iran the incidence of colorectal cancer has increased during the last 25 years.
  
  
  METHODS
  In this article we analyzed the survival of 447 colorectal patients of Taleghani hospital in Tehran using parametric competing-risks models. The cancers of these patients were diagnosed during 1985 - 2012 and followed up to 2013. The purpose was to assess the association between survival of patients with colorectal cancer in the presence of competing-risks and prognostic factors using parametric models. The analysis was carried out using R software version 3.0.2.
  
  
  RESULTS
  The prognostic variables included in the model were age at diagnosis, tumour site, body mass index and sex. The effect of age at diagnosis and body mass index on survival time was statistically significant. The median survival for Iranian patients with colorectal cancer is about 20 years.
  
  
  CONCLUSIONS
  Survival function based on Weibull model compared with Kaplan-Meier survival function is smooth. Iranian data suggest a younger age distribution compared to Western reports for CRC.
authors.affiliation: Department of Biostatistics, Faculty of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran E-mail : fajr_td@yahoo.com.
authors.forename: Ahmad Reza
authors.initials: AR
authors.lastname: Baghestani
authors.forename: Tahoura
authors.initials: T
authors.lastname: Daneshva
authors.forename: Mohamad Amin
authors.initials: MA
authors.lastname: Pourhoseingholi
authors.forename: Hamid
authors.initials: H
authors.lastname: Asadzadeh
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D015179:Colorectal Neoplasms / Q000209:etiology* / Q000401:mortality* / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009367:Neoplasm Staging; D011379:Prognosis; D012307:Risk Factors; D012737:Sex Factors; D015996:Survival Rate; D055815:Young Adult