title: The importance of long-term follow-up of head and neck cancer patients for reliable survival analysis.
abstract: OBJECTIVE
  Analyze the influence of patients lost to follow-up in estimated survival rates calculated by the Kaplan-Meier method.
  
  
  METHODS
  Only patients with previously untreated squamous cell carcinoma of the upper aerodigestive tract were selected. For the patients lost to follow-up anytime, the last medical evaluation date was collected to calculate the "estimate A" survival time. If the same patient returned to our outpatient clinic or further health information was obtained, the updated last information/evaluation date was also collected to calculate "estimate B" survival time. The survival curves considering "estimate A" and "B" survival rates were compared.
  
  
  RESULTS
  The overall 5 and 10-years survival rates for all patients calculated for "estimate A" were 54.0% and 46.0%, respectively; compared with 42.8% and 28.2% when were calculated considering "estimate B" (P < 0.001).
  
  
  CONCLUSIONS
  Close follow-up of the head and neck cancer patients is essential for an accurate estimate of survival by Kaplan-Meier method.
authors.affiliation: Head and Neck and Otorhinolaryngology Department, Centro de Tratamento e Pesquisa Hospital do Câncer A. C. Camargo, Sao Paulo, Brazil. priante@uol.com.br
authors.forename: Antonio Vitor Martins
authors.initials: AV
authors.lastname: Priante
authors.forename: André Lopes
authors.initials: AL
authors.lastname: Carvalho
authors.forename: Karina de Cássia Braga
authors.initials: Kde C
authors.lastname: Ribeiro
authors.forename: Hirde
authors.initials: H
authors.lastname: Contesini
authors.forename: Luiz Paulo
authors.initials: LP
authors.lastname: Kowalski
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000401:mortality* / Q000473:pathology; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000401:mortality* / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D010349:Patient Compliance; D012189:Retrospective Studies; D015996:Survival Rate / Q000639:trends; D013997:Time Factors