What is deduplication in cancer registries?

• A. Creating separate records for each tumor site to capture multi-site cases.
• B. Merging records that pertain to the same patient/case using identifiers, dates, sites, and histology to produce a single canonical record.
• C. Deleting records that lack unique identifiers.
• D. Merging records solely by patient name.

Answer: (B)

Deduplication in cancer registries is the process of merging records that refer to the same patient or cancer case into a single, canonical record. This ensures that each person and each cancer event is counted once and that information from multiple data sources is consolidated.

The best approach uses multiple matching points—such as patient identifiers, dates of diagnosis, tumor site, histology, and other key variables—to determine that records belong to the same case. When records match on these fields, they are merged into one unified record, with data reconciled as needed. This creates a complete, authoritative source per patient/case and prevents double counting.

Merging only by patient name or deleting records lacking perfect identifiers would either risk incorrect merges (confusing different people with the same name) or throw away valuable data, respectively. Creating separate records for each tumor site would fragment information and inflate counts, undermining data quality and comparability.

In practice, deduplication supports accurate incidence and survival statistics, consistent case histories, and reliable data for research and public health decision-making.