Data integration and interoperability are fundamental aspects of implementing the Observational Medical Outcomes Partnership Common Data Model (OMOP CDM). In the context of oncology, various data sources, such as cancer registries and epidemiological databases, generate data. These sources often use different data formats, structures, and standards, making comparability and analysis challenging. Metadata is crucial for this process, as it acts as a contextualized interface that facilitates the integration and harmonization of these diverse data sources. By establishing clear metadata standards, OMOP CDM ensures consistency in key attributes such as data types, reference formats, and data descriptions, which makes integration smoother and more effective. This standardization helps maintain data consistency and minimizes errors or misunderstandings that can arise from inconsistent data.