Negative immunomagnetic ex vivo purging combined with high-dose chemotherapy with peripheral blood progenitor cell autograft in follicular lymphoma patients: evidence for long-term clinical and molecular remissions

The feasibility and efficacy of a never immunomagnetic ex vivo negative pur ging method was evaluated on peripheral blood progenitor cells (PBPC) from 13 non-Hodgkin's lymphoma patients (eight follicular, FL; three mantle cell , MCL; two FL with histologic transformation). A peculiar feature of the st udy was the collection of PBPC after prolonged tumor debulking. Our method included a stem cell enrichment phase followed by cell Incubation with anti -B cell MoAbs (anti-CD19, CD20, CD22, CD23), addition of immunobeads, and t hen positive cell removal by passage on a Max-Sep (Baxter Immunotherapy) ce ll separator. Engraftment was rapid and stable. Hematological values were a ssessed 1 and 2 years after the autograft. Purging efficacy was molecularly assessed in a panel of 11 patients who showed persistence of POP-detectabl e lymphoma cells on PBPC harvests despite intensified chemotherapeutic debu lking. FOR-negativity was obtained in vitro and persisted in vivo after aut ograft in three FL patients; five more FL patients, whose purged PBPC were PCR+, converted to stable (3 patients) or fluctuating (two patients) PCR ne gativity after autograft. MCL patients never reached PCR negativity. Thus, ex vivo purging may have a role for FL patients harvesting PCR-positive PBP C after intensified chemotherapy. In contrast, the addition of ex vivo purg ing seems to be of little if any benefit far MCL patients.