In the era of personalized treatment in multiple myeloma, high-risk patients must be accurately defined. The International Myeloma Working Group recommends using the Revised International Staging System (R-ISS) to identify high-risk patients. The main purpose of our work was to explore the heterogeneity of outcome among R-ISS stage II patients assessing the impact of ISS, chromosomal abnormalities (CA) and LDH level in this subgroup. Data were issued from 1,343 newly diagnosed myeloma patients up to 65 years, enrolled in 3 clinical trials implemented by the Intergroupe Francophone du Myelome. All patients were eligible to an intensive treatment. Patients R-ISS stage II but ISS stage I had 1.6 times more risk of death than patients R-ISS stage I (adjusted HR 1.6; 95% CI, 1.1 to 2.2; P = .01) and patients R-ISS stage II but ISS stage III had a better overall survival than patients R-ISS stage III (adjusted HR 0.7; 95% CI, 0.4 to 0.9, P = .02). However, among patients classified in R-ISS II, ISS stage and CA (del(17p) and t(4;14)) were still relevant prognostic factors for death. Dividing R-ISS stage II into 3 subgroups: ISS I with standard risk CA, ISS II or III with standard risk CA and, high risk CA patients, median overall survivals were respectively not reached, 112 and 71 months (P < 0.001). In conclusion, stratification of patients in the R-ISS stage II group can be improved by taking into account CA and ISS. However, this does not improve predictive performance of survival models.
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