Abstract
Cancer stage at diagnosis is an important gap for Australian population based cancer registries. The study aims to understand the quality and completeness of three different collections of cancer staging data. The South Australian Cancer Registry data collection for breast and colorectal cancer (CRC) cases diagnosed in 2011, was linked to Registry Derived Stage (RDS) data, pathology plus hospital metastasis codes (pathology stage), and the South Australian Clinical Cancer Registry Stage (SACCR stage). The agreement between staging systems was examined using kappa statistics. Kaplan-Meier curves and Cox regression were used to examine the difference in survival by staging methods. Among 2,530 breast and CRC cases 98.8% were stageable (n = 2,500) according to histology. Among stageable cases, 84.6% had RDS, 51.2% had pathology stage and 29.5% had SACCR stage. The kappa statistic for RDS and pathology stage was 0.930 for breast cancer and 0.973 for CRC, and 0.574 for RDS and SACCR stage for breast cancer and 0.632 for CRC. The agreement between pathology stage and SACCR stage was 0.430 for breast cancer and 0.528 for CRC. The distribution of stage was similar across staging methods, although more stage four cancers by pathology stage, and survival patterns were similar but not the same. The agreement was high between different staging systems. Pathology stage had a higher than expected stage 4 proportion. This study highlights an opportunity to collect stage information in a cost-effective manner, while collecting data that usefully represent stage at diagnosis across the population, for population based epidemiological analyses.
Highlights
Cancer stage at diagnosis is an important gap for Australian population based cancer registries
The proportions were similar for breast and colorectal cancer for pathology stage (51.5% vs 50.8%) and South Australian Clinical Cancer Registry (SACCR) stage
When examining all available data, that is both data that were matched across the different staging systems and non-matched data, pathology stage has a significantly higher proportion of stage 4 cases when compared to Registry Derived Stage (RDS) and SACCR stage for breast cancer (Fig. 1)
Summary
Cancer stage at diagnosis is an important gap for Australian population based cancer registries. South Australia was a participant in the ‘National Collection of Registry Derived Stage for 2011’ project This project, led by Cancer Australia, examined the feasibility of Australian population based cancer registries meeting epidemiological demands for comparability and completeness in collecting disease stage at diagnosis for all eligible breast, lung, colorectal, melanoma and prostate cancers diagnosed in 2011 across Australia[9,10]. These data present an opportunity to evaluate the completeness and quality of the systematically collected population based www.nature.com/scientificreports staging data against other state based cancer staging systems in South Australia to better understand the value of the data collected from population based staging systems going forward
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