Persistent Monoclonality after Histological Remission in Gastric Mucosa Associated Lymphoid Tissue (MALT) Lymphoma Treated with Chemotherapy and/or Surgery: Influence of t(11;18)(q21;q21).

Background: The molecular response in patients with gastric MALT lymphoma achieving histological remission after chemotherapy with or without surgery is not well established.

Patients and Methods: 19 patients with gastric MALT lymphoma achieving complete histological remission after treatment with chemotherapy and/or surgery was studied retrospectively. IgV_H gene rearrangements were studied by PCR in gastric biopsies obtained at diagnosis and during follow-up. Presence of t(11;18)(q21;q21) was studied by FISH or PCR. Sequencing analysis of PCR products of patients with t(11;18)(q21;q21) was performed.

Results: t(11;18)(q21;q21) was present in 3 patients (15.7%) at diagnosis. Median follow-up was 73 months (13–240). In patients with complete histological remission, monoclonality was demonstrated in 11 out of 19 (58%) and maintained monoclonality in 8 out of 10 (80%) who had sequential studies. All 3 t(11;18)(q21;q21) positive patients had maintained monoclonality and sequencing analyses revealed the presence of the same mutated IgV_H alleles in diagnostic and in follow-up samples. In contrast, in 2 cases without t(11;18)(q21;q21) the monoclonal rearrangements corresponded to unrelated alleles. Persistent monoclonality was detected after a median of 49 months (6–134) and did not condition histological relapses, either in negative or positive t(11;18)(q21;q21) patients.

Conclusions: More than half of patients with gastric MALT lymphoma achieving histological response after chemotherapy and/or surgery have long term persistent monoclonality. t(11;18)(q21;q21) determines long term persistence of the initial lymphoma population. However, the presence of maintained monoclonality did not determine relapse.