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Absence of minimal residual disease detectable by FACS, Southern blot or PCR in patients with chronic lymphocytic leukaemia treated with fludarabine.

We report the results of assessment of minimal residual disease in four patients with chronic lymphocytic leukaemia, who achieved clinical and haematological complete response following treatment with fludarabine. Patients were assessed both before and after treatment by immunophenotyping, DNA electrophoresis, Southern blotting and PCR amplification to detect immunoglobulin gene rearrangements. Immediately after treatment, no patient had disease detectable by any method and there was evidence of recovery of normal B-cells. No patient has yet shown evidence of clinical or haematological relapse (follow-up 59-142 weeks). Two patients remain in immunophenotypic and molecular remission at 141 and 59 weeks. These methods have allowed more sensitive definition of elimination of residual disease, with PCR demonstrating the capacity to detect disease recurrence before any other evidence is available.