Cell free DNA and Cell tumor DNA
Non cell bound DNA fragments are shed into circulation as cell free DNA
(cfDNA). Circulating tumor DNA (ctDNA) which is cfDNA from tumor cells
is shed into blood through apoptosis, necrosis or through an active
process from neoplastic cells. Molecular aberrations in tumor tissues
such as point mutations, insertions, deletions and methylation profiles
are present in these circulating DNA fragments (55,56,57,58,59). The
fragmentation pattern of ctDNA in healthy people has been found to be
different from the pattern in patients with various kinds of cancers
(60). Surveillance circulating tumor DNA identifies patients at risk of
recurrence in DLBCL with a positive predictive value of 88.2% and
negative predictive value of 97ยท8% (61). Unlike CTCs and exosomes which
contain RNA and proteins together with DNA, ctDNA provides no proteomic
and transcriptomic information.
Immunoglobulin gene rearrangement is another novel technology for
identifying prognostic groups in DLBC. Molecular characterization of
immunoglobulin gene rearrangements revealed distinct subgroups in
non-GCB (62). DLBCL patients with immunoglobulin gene rearrangement have
been shown to have a lower rate of complete remission and significantly
poorer survival. (63).