Safety and Efficacy Of Abbreviated Induction With Only 4 Cycles Of Fludarabine (F), Cyclophosphamide (C) and Rituximab (R) In Physically Fit Patients With Chronic Lymphocytic Leukemia (CLL) Who Achieve Early Complete Remission (CR) With Undetectable Minimal Residual Disease (MDR)

Chemoimmunotherapy with 6 cycles of FCR is considered standard therapy for physically fit patients (pts) with Chronic Lymphocytic Leukemia (CLL). Many pts are unable to complete planned treatment, due to treatment related complications. Levels of minimal residual disease (MRD) have been shown to correlate with PFS in previously untreated patients with CLL (CLL8, Boettcher S et al. Leukemia, 2009). Achieving a negative MRD is therefore a mayor endpoint in treatment.

From 4/2003, 39 physically fit pts with CLL who had IWCLL-NCI criteria for initiating treatment started therapy with FCR in our institution. Eleven pts had previously received chlorambucil/prednisone and 28 were not previously treated. Median age at start of therapy was 63 years (34-80), Binet´s clinical stage were A/B: 22 pts (56%) and C: 17 (44%). The CD38 expression was positive (>7% of cells) in 23 (59%) and negative in16 (41%) of the pts.

After 4 courses of FCR response was assessed in peripheral blood (PB) or bone marrow (BM) using three colour flow Cytometry. Negative MRD was defined as < 0,1% of light chain restricted CD5+CD19+ B cells in PB and BM as assesed collecting 100000 CD19 cells in a three colour cytometer (FacsScalibur- blue laser ). All these patients stopped therapy after evaluation due to early CR with eradication of MRD.

All patients had negative MRD in peripheral blood, 35 were also evaluated in bone marrow, 29 showed CR and 6 nodular partial remission (NPR). Neutropenia and infectious events grade 3-4 were observed in 24% and 7% of all the courses respectively. No pts died of toxicity.

After a median follow-up of 81 months (4.6-120), progression free survival (PFS) and overall survival (OS) at 72 months was 51% and 75% respectively. Five pts died of progressive disease and 3 of a secondary neoplasm.

Stopping therapy in patients who achieve negative MRD after 4 cycles of FCR is safe and induces durable remission with a PFS and OS of 51% and 75% at 72 months exposing them to less chemotherapy. Large randomized trials are necessary to confirm this data.

Pavlovsky:Novartis: Speakers Bureau; BMS: Speakers Bureau.