Background. The objective of a population based cancer registry is considerably wider than presenting routine cancer incidence statistics. Registries are involved in epidemiological studies of causes of cancer, monitooring and evaluation of cancer screening, follow-up of cancer patients in relation of cancer care they receive. The quality of registry data is therefore utmost important.
Aim. The aim of the current paper is to provide an overview of the validity of Estonian Cancer Registry data in 1995–2008 and to compare validity indicators with other countries.
Methods. Cancer cases registered in Estonia in 1995–2008 were analysed. Percentages of microscopically verified cases (%MV), death certificate only cases (%DCO), cases detected at autopsy (%Autopsy) and cases with primary site unknown (%PSU) were calculated. The change in %MV, %DCO and %Autopsy in three time periods (1995–1999, 2000–2004 and 2005–2008) was examined. Validity indicators for 2003–2007 were compared with those from selected cancer registries of other European countries reported in „Cancer in Five Continents“ Volume X.
Results. The total number of analysed cases was 88 578. Overall, 87.2% of cases were microscopically verified, 1.7% were death certificate only cases, and 1.6% autopsy cases. %MV was lowest in pancreatic cancer (50.4%). DCO cases were most prevalent in cancer of heart, mediastinum and pleura (10.8%). Autopsy cases were most prevalent in mesothelioma (12.3%) and neoplasm of adrenal gland (12.1%). For five cancer sites (oesophagus; liver; pancreas; lung, trachea and bronchus, and heart, mediastinum and pleura), all three indicators were worse than the mean value calculated for all sites (%MV lower than the mean; %DCO and %Autopsy higher than the mean). In comparison of time periods, %MV remained stable for most cancer sites. As for %DCO, it increased during two first time periods for all sites, but remained below 3%, except for cancers of lung and pancreas (4.0% and 4.5% respectively). International comparison showed that %DCO (2.7% for men and 2.2% for women) and %PSU (2.7% for men and 2.4% for women) in Estonia were at high level, and %MV (84.7% in men and 87.9% in women) was close to the %MV of Western- European countries.
Conclusions. Our analysis demonstrated that the validity of Estonian Cancer Registry data is at favourable international level. Data quality of the registry relies on health care institutions sending cancer notifications. Improved completeness of notifying would decrease the number of back-tracings; fasten the routine work of the registry and publishing cancer statistics. Data completeness will be addressed in further publications.