In the Italian study, 56 of the 123 MBL cases progressed to fulfill criteria for overt CLL (n=37) or SLL (n=19). The median time to developing CLL/SLL was 55.0 months. Intuitively, and consistent with the report by Rawstron et al. (18), MBL cases with higher B-cell counts at MBL diagnosis were more likely to subsequently develop a B-cell count above the 5 x109/L threshold currently used to make the diagnosis of CLL.(27) Overall, 19 of 123 MBL cases progressed to symptomatic CLL/SLL requiring treatment, accounting for a 10-year treatment-free survival of 68.7%. In univariate analysis, IGHV gene mutation status (p<0.002), CD38 expression (p<0.001), CD49d expression (p=0.006), and cytogenetic abnormalities on FISH testing (p<0.001) all predicted treatment-free survival(TFS) among individuals with MBL. On multivariable analysis the presence of +12 or del(17p13) on FISH karyotype were the only independent predictors of TFS (HR=5.39, P=0.001).(27)
