Clinical relevance of high-risk cytogenetic abnormalities and the second revision of the International Staging System (R2-ISS) in patients with multiple myeloma in clinical practice.

High-risk cytogenetic abnormalities (HRCAs) are the most critical factor affecting prognosis in multiple myeloma (MM). However, the clinical significance of HRCAs in routine practice has not been fully elucidated. We retrospectively analyzed clinical features and outcome in 60 newly diagnosed MM patients with or without HRCAs including t(4;14), t(14;16), del(17p), and 1q gain/amplification. The median age was 71 years (range, 35-90). Abnormalities with t(4;14), t(14;16), del(17p), and 1q gain/amplification were found in 10, 1, 6, and 21/14 patients, respectively, and 10 patients had ≥ 2 HRCAs. Patients with HRCAs exhibited progressive clinical features such as anemia, high β2-microglobulin, and high LDH. Symptomatic relapse was more common in patients with HRCAs. The median progression-free survival (PFS) by number of HRCAs (0, 1, and ≥ 2) was 51.7, 21.4, and 26.1 months (p = 0.011), and the median overall survival (OS) was not reached, 60.7, and 46.8 months (p = 0.045), respectively. Multivariate analysis revealed that HRCAs were an independent factor for PFS. Accordingly, the second revision of International Staging System (R2-ISS), which incorporates HRCA scores, was more useful for prognostic stratification (p = 0.0023). These results suggest that presence of multiple HRCAs including 1q gain/amplification is associated with advanced stage and poor prognosis in clinical practice as well.