Rituximab and High-Dose Cytarabine Do Not Counteract the Adverse Prognostic Value of CDKN2A and TP53 Deletions in Autografted Mantle-Cell Lymphoma Patients. a European-MCL Network Study

Introduction

Mantle-cell lymphoma (MCL) is of poor prognosis, with a median survival of about 5 years. Besides the t(11;14) translocation, several secondary genetic abnormalities have been shown to correlate with prognosis. However, most studies have analysed patients with heterogeneous treatment, mostly with anthracyclin-based regimens. In 2004, the European MCL Network started the randomized MCL Younger trial comparing R-CHOP followed by high-dose radiochemotherapy and autologous stem cell transplantation (ASCT) versus alternating R-CHOP/R-DHAP followed by a high-dose cytarabine conditioning regimen and ASCT in previously untreated MCL stage II-IV patients up to the age of 65y. The R-CHOP/R-DHAP arm showed improved time to treatment failure (TTF) and, potentially, overall survival (OS) (Hermine et al., ASH 2010, ASH 2012). Our aim was to revisit the prognostic value of some gene copy number alterations (GCNA) in this randomized trial and to determine whether high-dose cytarabine could counteract some of those factors.

Methods

The inclusion criteria for this biological study were: confirmed histological diagnosis of MCL, the availability of diagnostic tumor DNA and complete clinical data. When no frozen biopsy was available, peripheral samples with more than 50% tumor cells were considered eligible for GCNA analysis. CDKN1B, CDK2, and MDM2 were analyzed using quantitative multiplex PCR of short fluorescent fragments (QMPSF) (Jardin et al., BJH 2009), 6q25-q26, CDK4, and the 13q14 locus were analyzed by multiplex ligation-dependent probe amplification (MLPA) (MRC-Holland CLL kit), and MYC, CDKN2A, ATM, RB1 and TP53 were assessed by both methods. The analyses of the prognostic value of GCNA was adjusted for clinical prognostic factors summarized in the quantitative MIPI score (age, performance status, LDH, and WBC). The rate of proliferating tumor cells (Ki-67 index) was centrally assessed by the reference pathologists of the European MCL Pathology Panel according to published guidelines (Klapper et al., J Hematopathol 2009). Outcome variables were TTF from treatment start to stable disease, progression, or death from any cause, and OS from trial registration to death from any cause.

Results

Of 135 patients fulfilling the inclusion criteria (median age 56 years), 49%, 26%, and 25% of patients were of low, intermediate, and high MIPI risk . The most frequent amplification involved MYC (18%), whereas the most frequent deletion involved the 13q14 locus (36%), including RB1 in 26%. As expected, CDKN2A and TP53 deletions were frequently found (25% and 22%, respectively). ATM alterations mostly consist of deletion (25%), but amplification was found in 3 of 129patients. The frequencies of GCNA did not differ according to the type of sample analyzed i.e. tumor biopsies (n=79) vs. high tumor load peripheral blood or bone marrow samples (n=56). The Ki-67 index was higher in patients with CDKN2A or RB1 deletion compared to patients without, but was not different between patients with or without TP53 deletion. Only TP53 gene status was associated with MCL cytology, with more frequent deletion in blastoid forms (4/8) than in classic MCL (11/81, 14%).

In univariable analyses, deletions of CDKN2A, 13q14, RB1, CDKN1B, and TP53 were associated with shorter TTF and OS, whereas GCNA of 6q25-q26, MYC, ATM, CDK2, CDK4, and MDM2 were not prognostic. In multivariable analyses, adjusting for MIPI score, CDKN2A and TP53 deletions showed independent prognostic impact with hazard ratios of 2.4 (p=0.001) and 2.3 (p=0.004) for TTF and 2.3 (p=0.007) and 2.4 (p=0.007) for OS. This effect was observed in both treatment arms (Figure 1). In addition, there was an interacting effect of CDKN2A (p16) deletion and TP53 deletion on TTF (p=0.004).

Conclusions

The introduction of high-dose cytarabine in first-line treatment of younger MCL patients did not erase the adverse prognostic value of TP53 and CDKN2A deletions observed with previous regimens. Moreover, our study identified a small patient group of very bad prognosis which could benefit of more aggressive regimens or new targeted drugs combination.

Figure 1:

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TTF (left) and OS (right) according to CDKN2A/TP53 deletion status in patients of the R-CHOP/R-DHAP study arm; nom=not deleted, del=deleted

Figure 1:

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TTF (left) and OS (right) according to CDKN2A/TP53 deletion status in patients of the R-CHOP/R-DHAP study arm; nom=not deleted, del=deleted

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