Translocation of t(14;18) and its importance infollow up of minimal residual disease in follicular lymphoma

Overview

The importance of t(14;18) reconstruction and better bcl-2/IgH reconstruction in the follow up ofminimal residual disease (MRD) in follicular lymphoma (FL) is not clear up to now. Plenty of reasonsare responsible for that. Low detection of t(14;18) by primer-specific PCR enables follow up of approximately60% of patients with FL. Some studies doubt correlation between molecular markers andclinical response. Reconstruction was found in a few other lymphoma types, including non-malignantlymphadenopaties and even in “healthy” individuals with varying detection between 15-50%. There isa question if bcl-2/IgH can be a suitable molecular marker for FL at all. Actually, according to detailedcytogenetic studies, there is an evidence that t(14;18) is sufficiently specific for follicular lymphomas.But original idea of the only two breakpoint regions does not corresponds to reality. While breakpointon the 14th chromosome is relatively constant, more than one third of breakpoints on 18th chromosomewas identified in the region between MBR and MCR. Logically, primer-specific nested PCR for MBRand MCR can not be effective for bcl-2/IgH determination. Some new and more difficult modificationsof PCR, as multiplexPCRand long-distance PCR, enable the detection of this reconstruction in 80-100 %.In addition to technical aspects, analysed compartment of residual disease has to be taken intoconsideration. The most measured compartment is peripheral blood because of it is easy available.There are few data definitely confirming that peripheral blood or bone marrow can reliably reflectdisease which originally arise in lymph nodes. Purpose of t(14;18) follow up in MRD in follicularlymphoma is to choose appropriate technology for its detection and then to test optimal compartmentfor molecular determination.

Key words:
follicular lymphoma, minimal residual disease (MRD), t(14;18), bcl-2/IgH