Evaluation of the Revised International Staging System in an independent cohort of unselected patients with multiple myeloma oleh Efstathios Kastritis, Evangelos Terpos, Maria Roussou, Maria Gavriatopoulou, Magdalini Migkou, Evangelos Eleutherakis-Papaiakovou, Despoina Fotiou, Dimitrios Ziogas, Ioannis Panagiotidis, Eftychia Kafantari, Stavroula Giannouli, Athanasios Zomas, Konstantinos Konstantopoulos, Meletios A. Dimopoulos