title: A model approach to calculate cancer prevalence from 5 year survival data for selected cancer sites in India.
abstract: BACKGROUND
  Prevalence is a statistic of primary interest in public health. In the absence of good follow- up facilities, it is difficult to assess the complete prevalence of cancer for a given registry area.
  
  
  OBJECTIVE
  An attempt was here made to arrive at complete prevalence including limited duration prevalence with respect to selected sites of cancer for India by fitting appropriate models to 1, 3 and 5 years cancer survival data available for selected population-based registries.
  
  
  METHODS
  Survival data, available for the registries of Bhopal, Chennai, Karunagappally, and Mumbai was pooled to generate survival for breast, cervix, ovary, lung, stomach and mouth cancers. With the available data on survival for 1, 3 and 5 years, a model was fitted and the survival curve was extended beyond 5 years (up to 35 years) for each of the selected sites. This helped in generation of survival proportions by single year and thereby survival of cancer cases. With the help of survival proportions available year-wise and the incidence, prevalence figures were arrived for selected cancer sites and for selected periods.
  
  
  RESULTS
  The prevalence to incidence ratio (PI ratio) stabilized after a certain duration for all the cancer sites showing that from the knowledge of incidence, the prevalence can be calculated. The stabilized P/I ratios for the cancer sites of breast, cervix, ovary, stomach, lung, mouth and for life time was observed to be 4.90, 5.33, 2.75, 1.40, 1.37, 4.04 and 3.42 respectively.
  
  
  CONCLUSIONS
  The validity of the model approach to calculate prevalence could be demonstrated with the help of survival data of Barshi registry for cervix cancer, available for the period 1988-2006.
authors.affiliation: National Cancer Registry Programme, (NCDIR), Bangalore, India E-mail : ramnath_takiar@yahoo.co.in.
authors.forename: Ramnath
authors.initials: R
authors.lastname: Takiar
authors.forename: Kasturi
authors.initials: K
authors.lastname: Jayant
mesh_terms: D003627:Data Interpretation, Statistical; D003710:Demography; D006801:Humans; D007194:India / Q000453:epidemiology; D015233:Models, Statistical; D009369:Neoplasms / Q000453:epidemiology* / Q000401:mortality*; D015995:Prevalence; D011379:Prognosis; D012042:Registries / Q000706:statistics & numerical data*; D012424:Rural Population; D015996:Survival Rate; D013997:Time Factors; D014505:Urban Population