Duration of complete remission. In the FCR cohort, patients with CLL cells that used mutated IgV_H (M-CLL) had significantly longer complete remission duration than did patients with CLL cells that used unmutated IgV_H (UM-CLL), despite similar proportions achieving complete remission. This effect was present both in the total population of complete responders (A) and in complete responders with negative marrow flow cytometry (B).