Bone Marrow BCL2/IgH+ Cells at Diagnosis and Not FCGRIIIA Polymorphism Predict Response in Follicular Non-Hodgkin’s Lymphoma Patients Treated with Sequential CHOP and Rituximab.

Background. The addition of Rituximab to chemotherapy significantly improves the clinical outcome in previously untreated follicular Lymphoma (FL) patients. Rituximab mediates its anti lymphoma effect by complement dependent cytotoxicity (CDC) and antibody dependent cellular cytotoxicity (ADCC). Genomic polymorphism corresponding to phenotype expression of valine (V) or phenylalanine (F) at amino acid 158 on the FcgRIIIA influences the affinity of IgG1 to this receptor and the ADCC activity played by NK cells, macrophages and neutrophils. The presence of a FcgRIIIA-158V on NK cells has been shown to be associated with a better clinical response after treatment with Rituximab in Follicular Lymphoma but not B-CLL patients.

Aim of the study. To correlate the achievement of a clinical and molecular response after the sequential treatment with CHOP and Rituximab with a) the presence of FcgRIIIA-158V/F polymorphism type in 88 previously untreated FL patients and b) the amount of follicular lymphoma cells detected at diagnosis in the bone marrow (BM) by quantitative PCR analysis of BCL2/IgH+ cells. Methods. FcgRIIIA-158V/F genotyping was performed using two different methods: a PCR with FRET probes and fluorescence melting curve analysis, on a LightCycler platform (Roche Diagnostics) and a Snapshot sequencing, using an ABI Prism 310 Genetic Analyzer (Applied Biosystems). Real Time Quantitative PCR (RQ-PCR) analysis of BCL2/IgH+ cells was performed using the ABI PRISM 7700 Detection System (Applied Biosytstems); standard curves were constructed using DNA from the cell line Karpas 422.

Results. Among the 88 patients analyzed for FcgRIIIA polymorphism, 17 were homozygous for V/V (19%); 30 patients were homozygous for F/F (34%) and 41 heterozygous for V/F (46%). A complete clinical response (CR) was obtained in 76% of patients homozygous for V/V and in 68% of patients carrying an FcgRIIIA F polymorphism (p=NS). A molecular evaluation performed on BM one year after the end of Rituximab administration was available for 63 patients. In this group a disappearance of BCL2/IgH+ cells in BM was observed in 30% of homozygous V/V patients and 58% of FcgRIIIA-F carriers respectively (p=NS). A similar result was also obtained when the molecular analysis was performed on peripheral blood (PB). The multivariate analysis did not show any association between FcgRIIIA polymorphism and the achievement of a clinical complete response or combined clinical and molecular response. As previously reported (Rambaldi et al, Blood 2005) the best predictor of clinical CR was the quantitative molecular evaluation of BM BCL2/IgH+ cells which at diagnosis was performed in 50 out of 88 patients analyzed for FcgRIIIA polymorphism (p < 0.02). The freedom from recurrence (FFR) of patients who achieved a molecular response in BM after CHOP and Rituximab administration was 50% as compared to 31% for patients who did not (p < 0.02).

Conclusions. FcgRIIIA polymorphism is not predictive of response for FL cases treated with sequential administration of CHOP-Rituximab. In this setting the quantitative evaluation of BCL2/IgH+ cells at diagnosis in BM remains the best predictor of clinical response. Moreover the achievement of a durable molecular response is associated with a better FFR.