Pharmacogenomic Markers of Clinical Efficacy in a Dose-Dense Therapy Regimen (R-CHOP14) in Diffuse Large B Cell Lymphoma

Abstract 2478

Diffuse large B cell lymphoma (DLBCL) is one of the most common types of non-Hodgkin's lymphoma. Approximately half of patients will be cured of their disease by primary therapy, including the R-CHOP regimen (rituximab, doxorubicin, cyclophosphamide, vincristine, desamethasone). The remaining die of the disease, mainly because of the occurrence of tumor drug resistance. Many efforts have been made to explain the biochemical and molecular mechanisms involved in resistance to the drugs used in the treatment of cancer patients, including those with DLBCL. A dose-intense therapy regimen (e.g. R-CHOP14) may help to improve the treatment outcome of DLBCL patients.

We have carried out a retrospective study aimed at correlating the mRNA expression levels of genes involved in metabolism, mechanisms of action and resistance to doxorubicin (i.e. MDR1, GSTP1, TOPO-2a, Bcl-2, PKC-b2) that represents the backbone of the R-CHOP regimen with treatment outcome data of 54 patients at various stages of disease.

The expression of the 5 above mentioned genes was determined in formalin-fixed paraffin-embedded samples from DLBCL using real time RT-PCR. A threshold analysis to identify a cut-off distinguishing recurrent or non-recurrent disease was used. The correlations between gene expression data and clinical/pathological characteristics as well as survival parameters have been evaluated by standard statistical tests.

The case series included 32 males and 22 females; 6 patients had follicular lymphoma grade IIIb and 48 diffuse large B cell lymphoma; 19 presented symptoms at diagnosis. Thirty patients showed abnormal LDH values, the IPI was intermediate-high risk or high risk in 14 patients. Forty-six patients (85.2%) obtained a complete remission and 8 (14.8%) a partial response.

The median overall survival (OS) as well as the median progression free survival (PFS) have not yet been reached after a median follow-up of 43.6 months.

The mRNA expression levels of TOPO-2a and GSTP1 were detectable in all samples, that of PKC-b2 in 52 samples, that of MDR1 and bcl-2 in 34 and 29 samples, respectively.

A high degree of interpatient variation in relative tumor expression of the study gene was observed: from 0.008 for TOPO-2a to >100.000 for PKCbII.

Threshold analysis indicated significant inverse relationships between PKC-b2 and PFS (p=0.046): higher gene expression was associated with shorter PFS. Conversely, higher expression of ABCB1 was associated with prolonged PFS (p=0.039). This kind of analysis also showed associations between OS and TOPO-2a, GSTP1and PKC-b2: higher gene expression was associated with shorter OS.

Overall, our results confirm that the high expression of some genes such as TopoIIa, GSTP1 and PKCβII may represent a prognostic factor in case of an intensified anthracycline-based chemotherapy with immunotherapy. Moreover, our results suggest that intensified immunochemotherapy could affect the role of bcl2, ABCB1, GSTP1 and TopoIIa in predicting tumor response.

These results and others from related studies may help to identify gene profiles useful for selecting patients eligible for more intensified or personalized chemotherapy. Prospective larger studies are warranted.

Supported by a grant from Associazione Giacomo Onlus, Castiglioncello (LI).