AT iwCLL MEETING
NEW YORK (FRONTLINE MEDICAL NEWS) – NOTCH1 gene mutation appears to predict reduced efficacy of ofatumumab in patients with relapsed/refractory chronic lymphocytic leukemia, according to an analysis of patient DNA samples and data from the phase III COMPLEMENT 2 trial.
Recurrent mutations in NOTCH1 , TP53 , and SF3B1 are common in CLL and have been associated with adverse outcomes in previous studies; NOTCH1 mutation, in particular, was associated with poor outcome when rituximab was added to standard chemotherapy, indicating that the mutation is a predictive factor in the context of chemoimmunotherapy, Eugen Tausch, MD , of the University of Ulm, Germany, said at the annual International Workshop on Chronic Lymphocytic Leukemia.
The incidence and clinical impact of all three mutations were evaluated in relapsed/refractory CLL patients who were part of the COMPLEMENT 2 trial, which compared fludarabine and cyclophosphamide (FC) with FC+ofatumumab (FCO).
The mutation analysis of 325 available patient samples (out of 365) identified 221 mutations in 142 patients: 56 NOTCH1, 96 TP53, and 69 SF3B1 mutations, Dr. Tausch said.
The current study cohort was representative of the full COMPLEMENT 2 analysis set, he noted.
Additional TP53 mutations were found in 20 of 61 TP53 mutation patients, whereas only 4 of 64 SF3B1 mutation patients and 3 of 53 NOTCH1 mutation patients had additional mutations in SF3B1 and NOTCH1, respectively. TP53 mutation was associated with del(17p) , and NOTCH1 mutation with +12q and elevated b2MG.
“We did not find associations with IGHV, gender, age, Binet stage, ECOG performance state, B symptoms, or WBC,” Dr. Tausch said.
In terms of outcomes as associated with the mutations, patients with TP53 mutation or SF3B1 mutation had a significantly worse overall response to treatment (overall response rate 67.8% vs. 84.4% for TP53 mutated vs. wild type, and 71.9% vs. 83.75% SF3B1 mutated vs. wild type, respectively). The findings were similar when looking at the treatment arms separately, he noted.
However, as in the full analysis set, progression-free survival among the subset of patients included in the current analysis was better in those who received FCO than in those who received FC (28.1 months vs. 18.1 months; hazard ratio, 0.67). TP53 mutation was an adverse prognostic factor overall in the current analysis (HR, 1.93), as well as in each treatment arm (HR for the FC arm, 2.14, and for the FCO arm, 1.81). TP53 mutation also was associated with decreased overall survival (HR, 2.11). Neither SF3B1 mutation nor NOTCH1 mutation were associated with differences in progression-free or overall survival, Dr. Tausch said.
CD20 expression on cell surface as measured using flow cytometry did not differ in wild-type vs. mutated patients, he said.
Multivariate analysis showed that independent prognostic factors for progression-free survival included FCO therapy (HR, 0.66), del(17p) (HR, 4.47), unmutated IGHV (HR, 2.17), and TP53 mutation (HR, 1.80), and independent prognostic factors for overall survival included del(17p) (HR, 5.02), unmutated IGHV (HR, 1.85), and TP53 mutation (HR, 1.68).
Adding ofatumumab to chemotherapy was beneficial, irrespective of TP53 mutation (HR, 0.52 for TP53 mutation, and HR, 0.68 for TP53 wild type), which confirms the prognostic value of TP53 mutation, he said.
With respect to NOTCH1, ofatumumab was beneficial in patients with NOTCH1 wild type but not in patients with NOTCH1 mutation (HR, 0.64 and 0.86, respectively).
This effect was not explained by CD20 expression levels, Dr. Tausch said.
The findings of this analysis suggest that NOTCH1 mutation is an independent predictive factor for reduced efficacy of ofatumumab, he said.
“Therefore, patients with a NOTCH1 mutation may be considered for chemotherapy without type1 CD20 antibodies or a treatment with novel compounds,” he concluded.
Dr. Tausch reported receiving research support from Novartis.
