Development of a Cytogenetic Double-Hit Model for Survival Prediction in Multiple Myeloma.

Background: High-risk chromosomal abnormalities (HRCAs) detected by fluorescence in situ hybridization (FISH) have a well-established adverse prognostic impact in multiple myeloma (MM). It is increasingly recognized that the coexistence of two or more HRCAs identifies a particularly poor-risk subgroup, often referred to as double- or multiple-hit MM. However, there is currently no consensus on its definition. Methods: We retrospectively analyzed a multicenter cohort of 1122 newly diagnosed MM patients from 2008 to 2019. Double-hit MM was defined as the coexistence of at least two of the following four HRCAs: t(14;16), gain(1q), del(17p), and del(1p). Based on this definition, we constructed a novel prognostic model, the HBDH (Institute of Hematology & Blood Diseases Hospital) double-hit model, and assessed its prognostic value for progression-free survival (PFS) and overall survival (OS). Results: According to the HBDH model, double-hit patients showed significantly inferior outcomes compared to non-double-hit patients, with median PFS of 20.6 vs. 53.3 months (p < 0.001) and median OS of 40.2 vs. 84.2 months (p < 0.001). The addition of del(13q), t(4;14), or t(11;14) did not improve the prognostic performance of the model. Importantly, the HBDH model was independent of the International Staging System (ISS), elevated LDH, and advanced age. Conclusions: The HBDH double-hit model identifies a subset of ultra-high-risk MM patients carrying at least two major HRCAs, providing a simple and robust framework for prognostic stratification and a potential reference for future biologically driven treatment approaches.