We characterized patients as having documented C1As or other high-risk chromosomal abnormalities (HRCAs) as defined by the Revised-International Staging System (R-ISS) such as del(17p), t(14;16), and t(4;14)….Compared with patients without C1As, patients with C1As were more likely to have higher stage (R-ISS stage III; 18% vs 12%), to have HRCAs (27% vs 14%), and to receive combinations of proteasome inhibitors and immunomodulatory agents (41% vs 34%). Median OS was lower for patients with C1As (46.6 vs 70.1 months; log-rank P < .001). C1As were independently associated with worse OS (adjusted hazard ratio, 1.42; 95% confidence interval, 1.19-2.69; P < .001)...