Next Generation Sequencing-based Validation of the Revised International Staging System for Multiple Myeloma: An Analysis of the MMRF CoMMpass Study

Introduction The clinical application of the Revised International Staging System (R-ISS) for multiple myeloma may be limited by heterogeneity in clinical interphase fluorescent in situ hybridization (FISH) practices for detecting chromosomal abnormalities (CAs). Next generation sequencing (NGS)-based FISH (Seq-FISH) has demonstrated improved sensitivity and similar specificity relative to clinical FISH, and provides a standardized, single-pass method for identifying high-risk CAs. To date, calculating R-ISS stage using Seq-FISH (R-ISS-NGS) has not been validated. Patients and Methods We identified 672 patients with sufficient data to calculate R-ISS-NGS from the Multiple Myeloma Research Foundation (MMRF) CoMMpass Study. R-ISS-NGS was calculated from original ISS stage, lactate dehydrogenase, and CAs detected by Seq-FISH. Endpoints included overall survival and progression-free survival. We conducted multivariate analyses controlling for age and gender in order to compare outcomes across stages I to III of both the original ISS and R-ISS-NGS. Results The median follow-up was 24 months. The R-ISS-NGS resulted in significant redistribution of patients into stage II, relative to the original ISS. With respect to stage I, R-ISS-NGS stages II and III of were associated with worse progression-free survival or overall survival, more so than the staging schema of the ISS, thus validating the use of Seq-FISH in staging. Conclusion Using CAs detected by Seq-FISH and data from the CoMMpass study, we validated the R-ISS with a large, generalizable cohort. This study validates the substitution of Seq-FISH for clinical FISH, especially in large registry studies. Additionally, use of the validated R-ISS-NGS will strengthen outcomes research generated from the CoMMpass study.