Impact of revised International Staging System 2 risk stratification on outcomes of patients with multiple myeloma receiving autologous haematopoietic stem cell transplantation

Summary The second revision of the International Staging System (R2‐ISS) is a simple tool to risk‐stratify newly diagnosed multiple myeloma (NDMM) patients. Here, we completed a retrospective analysis to evaluate the utility of R2‐ISS in NDMM patients who underwent up‐front autologous haematopoietic stem cell transplantation (auto‐HCT). A total of 1291 patients were included, with a median age of 62 years (range 29–83). The distribution of R2‐ISS stages was: 123 (10%) stage I, 471 (36%) stage II, 566 (44%) stage III and 131 (10%) stage IV. With a median follow‐up of 42.2 months (range 0.3–181.0), the median PFS was 73.0, 65.2, 44.0 and 24.8 months, ( p < 0.001) and the median OS was 130.8, 128.5, 94.2 and 61.4 months ( p < 0.001) for patients with R2‐ISS stages I, II, III and IV respectively. On multivariable analysis (MVA) for PFS, using R2‐ISS stage I as reference, R2‐ISS stages III (hazard ratio [95% confidence interval], 1.55 [1.05–2.29]; p = 0.028) and IV (2.04 [1.24–3.36]; p = 0.005) were associated with significantly inferior PFS. In the MVA of OS, using R2‐ISS stage I as reference, only R2‐ISS stage IV was associated with significantly inferior OS (2.43 [1.18–5.01]; p = 0.017). Overall, we found that R2‐ISS is a reliable prognostic tool for NDMM patients undergoing up‐front auto‐HCT.