A method for differentiating cancer prevalence according to health status, exemplified using a population-based sample of Italian colorectal cancer cases

Abstract Cancer prevalence is the proportion of a population diagnosed with cancer. We present a method for differentiating prevalence into the proportions expected to survive without relapse, die of cancer within a year, and die of cancer within 10 years or survive with relapse at the end of the 10th year. Material and methods. The method was applied to samples of colorectal cancer cases, randomly extracted from four Italian cancer registries (CRs). The CRs collected data on treatments, local relapses, distant relapses, and causes of death: 1) over the entire follow-up to 31 December 2007 for 601 cases diagnosed in 2002 (cohort approach); 2) over a single year (2007) for five cohorts of cases defined by year of diagnosis (from 1997 to 2001), alive at 1 January 2007 (total 298 cases). The cohorts were combined into a fictitious cohort with 10 years survival experience. For each year j after diagnosis the health status of cases alive at the beginning of j was estimated at the end of the 10th year. From these estimates the 10-year colorectal cancer prevalence was differentiated. Results. We estimated: 74.7% alive without relapse or not undergoing treatment at the end of 10 years; 8.1% had died of colorectal cancer within a year; 11.4% had died of colorectal cancer 1-10 years after diagnosis or had relapsed or were undergoing treatment at the end of the 10th year; and 5.8% had died of other causes. Conclusions. We have introduced a new method for estimating the healthcare and rehabilitation demands of cancer survivors based on CR data plus treatment and relapse data specifically collected for samples of cases archived by CRs.