Predictive value of 1q21 gain in multiple myeloma is strongly dependent on concurrent cytogenetic abnormalities and first-line treatment.

Improved therapies in multiple myeloma (MM) have forced a constant risk stratification update, first Durie-Salmon, then international scoring systems (ISS), next revised-ISS (RISS) including high-risk cytogenetic abnormalities (HRCAs) such as del(17p) and t(4;14), and now R2-ISS including 1q21 gain has been proposed. Predictive value of 1q21 gain by itself or in concurrence with other cytogenetic abnormalities is evaluated in 737 real-world plasma cell neoplasm (PCN) patients under current therapies. Ten-year progression-free survival (10y-PFS) rates for patients with 2, 3 and >3 copies of 1q21 were 72.2%, 42.5% and 43.4% (P<1.1×10). Cox regression analysis confirmed that 1q21 gain was an independent prognostic factor for PFS (HR=1.804, P<0.0001, Harrell C-statistic =0.7779±0.01495) but not for OS (P=0.131). Gain of 1q21 was strongly associated with hypodiploidy (38.8% vs. 7.0%, P=1.3×10), hyperdiploidy (44.1% vs. 16.4%, P=1.6×10), HRCAs (12.6% vs. 3.5%, 1.8×10), IGH breaks (12.3% vs. 2.1%, P=2.1×10) and del(13q) (8.0% vs. 4.0%, P=0.031). In our series, 1q21 gain by itself did not improve RISS predictive capacity in patients either eligible or ineligible for autologous stem cell transplantation (ASCT). However, compared with patients with other 1q21 gains: concurrence with hyperdiploidy improved the prognosis of ASCT-eligible patients from 62.5% to 96.0% 10-year overall-survival (10y-OS, P<0.002); concurrence with hypodiploidy improved the prognosis of ASCT-ineligible patients from 35.7% to 71.0% (P=0.013); and concurrence with del(13q) worsened the prognosis of ASCT-ineligible patients from 12.5% to 53.4% (P=0.035). Gain of 1q21 should be patient-wisely evaluated, irrespective of the RISS, considering its concurrence with other cytogenetic abnormalities and eligibility for ASCT.