A UK multicentre phase II study of rituximab (chimaeric anti-CD20 monoclonal antibody) in patients with follicular lymphoma, with PCR monitoring of molecular response.

Follicular lymphoma (FL) cells express CD20 and are associated in most cases with the t(14;18) chromosomal translocation. A multicentre study was undertaken between January 1997 and January 1998 to assess the complete response rate (CR) and overall response rate (RR) to rituximab, a chimaeric anti-CD20 monoclonal antibody. Seventy patients with previously treated FL received rituximab (375 mg/m2/week x4, by intravenous infusion). Restaging studies were performed 1 and 2 months after therapy. Molecular monitoring for the presence of cells harbouring the Bcl-2/JH gene rearrangement in the peripheral blood (PB) and bone marrow (BM) was performed before and after treatment using a two-step semi-nested polymerase chain reaction (PCR) assay. The overall RR was 32/70 (46%), being highest in patients who had received only one previous treatment (12/15, 80%). However, only two patients achieved a CR. The median duration of response was 11 months. Thirteen of 21 evaluable 'PCR-positive' patients (62%) became 'PCR-negative' in PB and/or BM samples 1 month after rituximab, although this did not correlate with clinical response. Treatment was generally well tolerated, although one patient developed Stevens-Johnson syndrome. Rituximab was shown to be active in FL, and in some cases PB and/or BM became PCR negative. Studies in combination with cytotoxic chemotherapy to increase the CR rate are warranted.