A WHO CNS5-Aligned Classification Framework for Population-Based Surveillance of Brain and Other Central Nervous System Tumors in the United States

Background

The Central Brain Tumor Registry of the United States (CBTRUS) uses a histology grouping model based on the World Health Organization (WHO) to classify cancer registry records for clinically relevant statistical reporting.

Methods

CBTRUS, together with its consulting neuropathologists, reviewed and aligned its histology groupings with the 2021 WHO Classification update. Obsolete histology nomenclature along with their International Classification of Diseases for Oncology 3 ^rd edition (ICD-O-3) codes were identified, currently included histologies were reclassified as appropriate, and new codes found in 2021 WHO were incorporated. An evaluation was conducted of the frequency of histology codes affected in the reclassification process, as well as incidence and survival pre- and post-reclassification of CBTRUS Tumor Type Groupings.

Results

After review of the CBTRUS grouping scheme, 205 codes were reclassified and 2 new codes were incorporated. Tumor type groups most affected were those classified as glioma. Reclassification resulted in 167,038 of 491,804 (34%) cases having a grouping reclassification or reporting change, indicating that the 2021 revision of the WHO Classification has significantly impacted the collection and reporting of primary b CNS tumors.

Conclusion

This work demonstrates the need to be responsive to changes in classification and coding for statistics to reflect real-world clinical use. This will require collaboration from all parties to have the ability to reconcile clinical practices and surveillance requirements.

KEY POINTS

• Classification changes in cancer registration pose challenges to reporting clinically-relevant population-based epidemiologic statistics for central nervous system (CNS) tumors.

• The Central Brain Tumor Registry of the United States provides an example of aligning ICD-O-3 and 2021 WHO CNS classification with cancer registry reporting.

• Implementation of ICD-O-4 and the latest WHO (CNS6) will undoubtedly be challenging to cancer registry reporting yet will ultimately improve our understanding of these tumors and their impact on a population.

IMPORTANCE OF THE STUDY

We performed this study to report on the Central Brain Tumor Registry of the United States (CBTRUS) tumor classification scheme which was revised to make it consistent with the 2021 WHO classification (CNS5) revision and to provide a roadmap for implementation of the recently published ICD-O 4 ^th edition. While we have previously published descriptive epidemiology for selected entities based on the CNS5 classifications, this is the first CBTRUS grouping scheme to include molecular information coded in the Brain Molecular Marker Site-Specific Data Item.

LAY SUMMARY

Central nervous system (CNS) tumor classification systems help doctors, researchers, and cancer registries identify and track specific types of CNS tumors. When the World Health Organization (WHO) updated its CNS tumor classification in 2021, the Central Brain Tumor Registry of the United States (CBTRUS) reviewed and updated its reporting system to match these changes. More than 200 tumor codes were reclassified, affecting nearly one-third of CNS tumor records, and most heavily impacted gliomas. These updates improve the accuracy and clinical relevance of national CNS tumor statistics. Ongoing collaboration among treating physicians, pathologists, cancer registries, and researchers will be essential as future classification updates are implemented.