Population Based Studies of Cancer Survival: Scope for theDeveloping Countries

Survival refers to the life of a person after diagnosis of disease, and survival studies have the objective ofevaluating the overall performance of a group of patients in terms of quality and quantity of life after the diagnosisor treatment. Potentially there are two approaches for the study of population-based survival; direct (classical)and indirect. The direct approach refers to defining a cohort of patients and collecting follow-up information,whereas the indirect approach uses current data on incidence and mortality for estimating various segmentsof life. In general, there are numerous difficulties in the conduct of population-based survival studies by theclassical method, especially in the set-up of developing countries. These include time and finance required forthe conduct of the study, the problem of loss to follow-up and also the time gap between the year of diagnosis ofpatients and the availability of results on their survival. In fact the problem of time gap is recognized even in thedeveloped world. There have been many studies highlighting these problems and suggesting potential solutions.Generally they have focused on three directions: viz, improving the address information and thereby reducingthe loss to follow-up; development of methodologies to deal with the losses to follow-up and indirect studies ofcancer survival, thereby obviating the follow-up process. This commentary covers the potential approaches ofpopulation-based survival studies, classical survival studies, problems in the same, and methods adopted fortheir solution. A summary of the conceptual and methodological developments on these concepts, highlightingthe scope for the developing countries, is also presented.