Risk of Central Nervous System (CNS) Involvement in Patients with Mantle Cell Lymphoma (MCL): Analysis of Clinico-Biological Factors in a Series of 283 Cases

Introduction:

MCL is a mature B-cell neoplasm characterized by t(11;14) (q13;q32) and cyclin D1 (CCND1) overexpression. Molecular studies have revealed other alterations in cell-cycle regulation, DNA damage response and cell survival pathways, with a landscape of somatic mutations being recently identified.

CNS involvement is a well known complication, occurring in 4-26% of MCL at five years, with an ominous significance. Although different clinical variables have been identified as risk factors for CNS infiltration, the biological parameters related to this complication have not been extensively studied. The aim of the study was to explore the biological parameters associated with CNS involvement in a multicentre and retrospective series of MCL patients.

Patients and Methods:

285 patients (M:74%; 64 yr) diagnosed of MCL between 1990-2014 (median survival of 4 years) were analysed. In addition to standard clinico-biological variables, IGHV mutational analysis, chromosomal alteration studies and Sanger sequencing of NOTCH1, NOTCH2, TP53, BIRC3, WHSC1, MEF2B, MLL2, TLR2 and PRDM1 were performed.

Results:

CNS involvement was observed in 15/285 MCL patients (5.2%), with a 5-yr risk of 9.1% (95%CI: 4.6-13.6), one patient at diagnosis, and at first or second/ulterior progressions in 7 cases each. The clinical, pathological and molecular risk factors identified are detailed in the Table. In addition to what has been already described, CNS involvement was usually observed in MCL cases with a clinical nodal presentation (p=0.05). In fact, no indolent MCL with a non-nodal presentation developed this complication during the follow-up period. No differences were observed in the risk of CNS involvement between patients treated in first-line with conventional or high-dose intense treatment (5-yr risk: 6.1%+/-6% vs. 10.7%+/-10.6%, p=ns).

Regarding the biological features, no differences in terms of the IGHV mutational status were observed in cases developing CNS involvement compared to the others (75% vs. 68.7%, using 97% identity cut-off). Similarly, the IGHV gene usage of CNS involved cases corresponded to the more frequent IGHV genes observed in MCL (usually IGHV1-18, IGHV3-23, IGHV4-34, IGHV4-59). Although not significant, a predominance of high number copy number alterations (CNA) (>4) could be observed in the genetic study of MCL cases with CNS involvement as could be expected for the enrichment in blastoid variants (up to 50% of these cases). In fact, we did not observe any case with CNS involvement among those cases with 3 or less CNA. CNS involvement was not related to common poor prognosis genetic alterations such as 9p, 11p and 17p losses, but the presence of 8q gains was associated with a higher risk of CNS involvement (p=0.05). We did not find any significant association between CNS involvement and the large number of oncogenic mutations studied.

Conclusions:

CNS involvement in MCL is associated with initial aggressive clinico-biological characteristics. Non-nodal MCL cases with a low number of genetic alterations did not present CNS involvement. Finally, the presence of 8q gains was associated with a higher risk of CNS infiltration.

CNA: copy number alteration; IGHV: immunoglobulin heavy chain; LDH: Lactate dehydrogenase