Outcome of Treatment with Fludarabine Versus Fludarabine and Cyclophosphamide in Chronic Lymphocytic Leukemia (CLL) Is Adversely Impacted by High Risk Genetic Features: Results from ECOG 2997.

Several prognostic factors including un-mutated V_H mutational status, select interphase cytogenetic abnormalities [del(11q22.3), del(17p13.1)] and p53 mutations have been associated with shorter interval time from diagnosis to symptomatic disease requiring treatment, shortened progression-free survival (PFS) and overall survival (OS). Limited prospective data exists relative to the relevance of these biologic markers on PFS following treatment with modern therapies for CLL. E2997 is a randomized phase III trial of 278 previously untreated, symptomatic CLL patients who received fludarabine and cyclophosphamide (FC) versus fludarabine (F). We analyzed the response rates and PFS of the patients for whom interphase cytogenetics, V_H mutational status, and p53 mutational status studies have been completed. FC therapy had a higher complete response (CR) (23% versus 5%, p<0.002), overall response [OR] (73% versus 50%, p<0.002), and median PFS (33.5 months versus 15 months, p<.0001) as compared to F. The CR and OR was not different based upon interphase cytogenetics or V_H mutational status for the entire group of patients or when analyzed by arm of treatment. However, the OR for pts with del(17) or p53 mutations was lower in both the FC arm (69%, versus 76% in patients with normal p53) and F arm (27%, versus 54% in normal p53). Using the Dohner hierarchical classification [del(17p)>del(11q)>del(6q)>tri12>normal> del(13q14)], the relationship of interphase cytogenetics, V_H mutational status and p53 mutational status with PFS is summarized below:

Using the interphase cytogenetic groups, there was a significant difference in PFS for both the FC (p=0.04) and F (p=0.01) treatment arms. Similarly, the presence of a p53 mutation or deletion [del(17p)] predicted for shorter PFS for both FC (p=0.005) and F (p=0.02) therapies. PFS did not statistically differ among V_H mutational groups for either arm. We next investigated a Cox proportional hazards analysis to assess the impact of multiple molecular features and treatment arm on PFS. Treatment with F (hazard ratio 3.14, p<0.0001), presence of del(17p) or p53 mutation (hazard ratio 3.13, p=0.0001), and presence of del(11q) (hazard ratio 2.067, p=0.019) were highly significant in the model. Finally, V_H unmutated status and del(11q) were highly associated. In conclusion, our data demonstrate that high risk genomic features including p53 mutations, del(17p), and del(11q) are highly predictive of shortened PFS. Our data provide support for a risk-stratified therapy approach for the treatment of CLL.