For population-based cancer registries, stage is becoming a cornerstone because it permits calculation of survival, assessment of the results of screening programmes and inter-hospital performance comparisons.
Stage 1 has been present since the Registry commenced, stage 2 was introduced in 2003, and stage 3 in 2007.
Confounding factors such as registry completeness, stage migration and distribution, diagnostic improvements and lead-time bias have to be considered when analyzing trends in cancer survival.
Medical coders from the Registry categorise stage based on information from statutory notification forms and pathology reports using a modified summary classification similar to the Surveillance, Epidemiology, and End Results (SEER) summary stage [ 21].
The type, completeness, and coverage of data collected by a registry, its stage of development, the strategies used for internal and external data validation, the approach to analysis, and importantly the issue being addressed by that analysis all contribute to the relative value of the data compared to other registry data.
It may be possible to create an algorithm using administrative data that mimics more closely the rules of the cancer registry for stage I patients who receive polypectomy rather than an inpatient surgery; the current study, however, was focused on the comparability of the data sources specifically using surgery codes from the administrative data sources.
Restricting the adjusted analysis to cancer registries where stage recording was 85% complete also had little impact on the results.
In regional cancer registries, the stage at diagnosis was not reported in 35% to 40% of prostate cancer cases, but distant metastasis at diagnosis was reported in 15% to 17% of the remaining cases [20], [22]– [22].
Stage at diagnosis was determined using the cancer registry and/or FIGO stage information from each site (SEER guidelines: http://seer.cancer.gov/) and categorised as FIGO stage I/II (localised and regional) and FIGO stage III/IV (distant).
iHRs adjusted for age and year at diagnosis, race, SEER registry, tumor histology, stage, grade, and surgical and radiation treatment.
