title: Incidence and nature of CD20-negative relapses following rituximab therapy in aggressive B-cell non-Hodgkin's lymphoma: a retrospective review.
abstract: Re-treatment with rituximab for B-cell non-Hodgkin's lymphoma (NHL) relapsing after previous rituximab therapy has recently been shown to be clinically efficacious. Although the mechanism of resistance to rituximab re-treatment in non-responding patients is unknown, it is possible that loss of CD20 expression in the relapsed NHL could be important in some patients. We examined the incidence and nature of CD20 negative relapses following rituximab therapy in aggressive B-cell NHL treated at our institution. Of a total of 18 patients who received rituximab, 13 have relapsed, with 10 patients subsequently undergoing repeat tissue biopsy. Six of these 10 patients (60%) were shown to have lost CD20 expression by either immunohistochemistry and/or flow cytometry. Furthermore, three of the six patients who relapsed with CD20-negative NHL also suffered relapses at unusual anatomical sites. We conclude that loss of CD20 expression in aggressive B-cell NHL relapsing post-rituximab therapy is common. As such, repeat tissue biopsy should be undertaken to document CD20 expression by both flow cytometry and immunohistochemistry prior to considering repeated courses of rituximab in relapsed aggressive lymphomas.
authors.affiliation: Department of Haematology, Royal Brisbane Hospital, Australia. Glen_Kennedy@health.qld.gov.au
authors.forename: Glen A
authors.initials: GA
authors.lastname: Kennedy
authors.forename: Siok-Keen
authors.initials: SK
authors.lastname: Tey
authors.forename: Ralph
authors.initials: R
authors.lastname: Cobcroft
authors.forename: Paula
authors.initials: P
authors.lastname: Marlton
authors.forename: Gavin
authors.initials: G
authors.lastname: Cull
authors.forename: Karen
authors.initials: K
authors.lastname: Grimmett
authors.forename: Damien
authors.initials: D
authors.lastname: Thomson
authors.forename: Devinder
authors.initials: D
authors.lastname: Gill
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000032:analysis* / Q000276:immunology; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D015994:Incidence; D016393:Lymphoma, B-Cell / Q000188:drug therapy / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy / Q000276:immunology*; D012189:Retrospective Studies; D000069283:Rituximab
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D000970:Antineoplastic Agents; D000069283:Rituximab