A Model Approach to Calculate Cancer Prevalence From 5 Year Survival Data for Selected Cancer Sites in India

Background: Prevalence is a statistic of primary interest in public health. In the absence of good followupfacilities, it is difficult to assess the complete prevalence of cancer for a given registry area.
Objective: Anattempt was here made to arrive at complete prevalence including limited duration prevalence with respect toselected sites of cancer for India by fitting appropriate models to 1, 3 and 5 years cancer survival data availablefor selected population-based registries. Materials and
Methods: Survival data, available for the registries ofBhopal, 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 andthe survival curve was extended beyond 5 years (up to 35 years) for each of the selected sites. This helped ingeneration of survival proportions by single year and thereby survival of cancer cases. With the help of survivalproportions available year-wise and the incidence, prevalence figures were arrived for selected cancer sites andfor selected periods.
Results: The prevalence to incidence ratio (PI ratio) stabilized after a certain duration for allthe cancer sites showing that from the knowledge of incidence, the prevalence can be calculated. The stabilizedP/I ratios for the cancer sites of breast, cervix, ovary, stomach, lung, mouth and for life time was observed tobe 4.90, 5.33, 2.75, 1.40, 1.37, 4.04 and 3.42 respectively.
Conclusions: The validity of the model approach tocalculate prevalence could be demonstrated with the help of survival data of Barshi registry for cervix cancer,available for the period 1988-2006.