BACKGROUND: Postmarketing drug safety surveillance studies can be used to monitor drug safety but require large sample sizes to detect small increases in risk when assessing the combination of an infrequent drug exposure and a rare cancer outcome. Linking data from multiple state cancer registries to large pharmacy databases can potentially address these issues.
OBJECTIVE: To describe the methods for two parallel but separate studies that implemented linkages between participating state cancer registries and two large United States pharmacy databases (either the Medicare Part D prescription claims database or a large commercial prescription dispensing database [IQVIA LRx]).
METHODS: All state cancer registries were invited to participate in both studies. Exposure and comparator cohorts were created using either Medicare Part D data (aged 65+) or LRx data (aged 18+). Both studies utilized trusted third parties (TTPs) to perform the linkages. Linkage with Medicare required registries to send encrypted data to Medicare’s TTP, while linkage with LRx required registries to either send identifiable data via secure FTP that was then deidentified and encrypted by IQVIA’s TTP or install deidentification and encryption software locally and send data to the TTP.
RESULTS: For the Medicare linkage, 26 registries participated, covering 68% of osteosarcoma cases aged 65+, while for the LRx linkage, 29 registries participated, covering 70% of osteosarcoma cases aged 20+. Reasons why registries could not participate in one or both studies included inability to send identifiable data externally, inability to install software locally, lack of resources/interest, and/or the inability of TTPs to sign registry data use and/or confidentiality agreements. Challenges among participating registries included working through local registry restrictions for sharing identifiable data, gaining permission to install external software, and/or completing contractual agreements that aligned with TTP and data holder requirements.
CONCLUSIONS: Varying requirements and the logistics of working with state entities, the federal government, and a commercial database made the study complex and resource- intensive. However, linking registry data to pharmacy databases can be an effective way to conduct safety studies investigating rare drug exposures that also require validated outcomes for a rare cancer.
