Specific p53 mutations do not impact results of alemtuzumab therapy among patients with chronic lymphocytic leukemia

Remission maintenance treatment options in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) treatment has come a long way in the last two decades, producing increases in tumor control to the point of generating sizeable numbers of patients with undetectable minimal residual disease and creating overall survival benefits in randomized comparisons. Most of this has been achieved by limited-term treatment approaches including chemotherapeutic and immune-therapeutic drugs. More recently, novel therapies targeting signaling pathways essential for the survival of the neoplastic clones have opened avenues that provide disease control in long-term treatment designs, mostly without producing deep remissions. In this disease, where current treatments are largely unable to effect a cure, prolonged therapy designs using maintenance approaches are explored and 5 randomized studies of maintenance have recently been published. This review shall summarize available results from a systematic literature review in a clinical context and outline basic biology principles that should be heeded in this regard.

The outcome of chronic lymphocytic leukemia patients who relapsed after fludarabine, cyclophosphamide, and rituximab

BACKGROUND

There are minimal data about the efficacy of subsequent therapy in patients with relapse after FCR (fludarabine, cyclophosphamide, and rituximab) chemoimmunotherapy.

METHODS

We retrospectively analyzed the outcomes of 119 patients who relapsed after standard-dose FCR. The patient cohort consisted of patients who relapsed after FCR administered as first-line therapy (Group 1, n = 63) and patients relapsing after FCR administered in second/subsequent line; (Group 2, n = 56).

RESULTS

Basic parameters (age, clinical stage, cytogenetics, molecular genetics) did not differ significantly between these subgroups. Likewise, median progression-free survival (PFS) was not considerably different after FCR (18.6 vs. 14.7 months). Subsequent therapy for relapsed disease included FCR retreatment, R-CHOP, alemtuzumab, or rituximab plus high-dose dexamethasone. Overall response rates for the two groups did not significantly differ (59% vs. 44%). Although PFS after subsequent therapy was relatively short, longer PFS was observed in Group 1 (13.3 vs. 5.9 months; P = 0.01), in patients with response duration ≥ 24 months after previous FCR (13 vs. 6.1 months; P < 0.01), and in patients who achieved complete remission after FCR (10.8 vs. 7.9 months in partial remission; P = 0.01). Newly detected 17p deletions were observed in 5/62 patients, and new p53 mutations in 6/34 FCR-treated patients.

CONCLUSION

Our data indicate that the prognosis of patients who relapse after FCR remains poor regardless of the subsequent treatment regimen.

TP53 aberrations in chronic lymphocytic leukemia

CLL patients harboring TP53 defects remain the most challenging group in terms of designing rational and effective therapy. Irrespective of the treatment employed-chemotherapy, chemoimmunotherapy, or pure biological drugs-median survival of these patients does not exceed 3-4 years. This adverse outcome is caused by a less effective response to therapeutics acting through DNA damage induction and relying on the subsequent initiation of apoptosis as well as by virtually inevitable aggressive relapse. Patient proportions with TP53 defects at diagnosis or before first therapy were reported within the range 5-15 %, but they increase dramatically in pretreated cohorts (reported up to 44 %), and also in patients with Richter transformation (50 % harbor TP53 defects). Currently, most laboratories monitor TP53 defect as presence of 17p deletion using I-FISH, but 23-45 % of TP53-affected patients were shown to harbor only mutation(s). In other patients with intact TP53, the p53 pathway may be impaired by mutations in ATM gene coding for the p53-regulatory kinase; however, prognosis of ATM-defective patients is not as poor as those with TP53 abnormalities. Though many novel agents are under development, the monoclonal antibody alemtuzumab and allogeneic stem cell transplantation remain the basic treatment options for TP53-affected CLL patients.