Clonotypic polymerase chain reaction confirms minimal residual disease in CLL nodular PR: results from a sequential treatment CLL protocol

Patient-tumor-specific oligonucleotides were generated for the detection of minimal residual disease (MRD) in a highly specific and sensitive clonotyp ic polymerase chain reaction (cPCR), The clone-specific region of highest d iversity, CDR-III, was PCR amplified and sequenced. Nested CDR-III clonotyp ic primers were used in a semi-nested cPCR with a sensitivity of at least 1 in 10(5) cells. Patients with protocol-eligible Rai intermediate or high-r isk chronic lymphocytic leukemia (CLL) received induction with fludarabine 25 mg/m(2) per day for 5 days every 4 weeks for 6 cycles, followed by conso lidative high-dose cyclophosphamide (1.5, 2.25, or 3g/m(2)). cPCR was perfo rmed on peripheral blood and bone marrow mononuclear cells. All 5 patients achieving a clinical partial remission (PR) studied by cPCR were positive. Five patients achieved nodular PR (nPR) (residual nodules or suspicious lym phocytic infiltrates in a bone marrow biopsy as the sole suggestion of resi dual disease). Five of 5 patients with nPR were cPCR positive. In contrast, flow cytometry for CD5-CD19 dual staining and kappa-lambda clonal excess d etected MRD in only 3 of the same 5 nPR patients, all of whom were cPCR pos itive, and immunohistochemistry detected MRD in only 1 of 4 assessable pati ents. Three of 7 CR patients evaluable by cPCR had MRD. Only 1 OR patient h ad MRD by flow cytometry; that patient was also cPCR positive. These data s upport the conclusions that nodular PR in CLL represents MRD and that clono typic PCR detects MRD in CLL more frequently than flow cytometry or immunoh istochemistry. (Blood.2001;97:1929-1936) (C) 2001 by The American Society o f Hematology.