Minimal residual disease (MRD) was evaluated in 30 patients with follicular or mantle cell non-Hodgkin's lymphoma (NHL) undergoing an intensive treatment with high-dose sequential (HDS) chemotherapy and peripheral blood progenitor cell (PBPC) autografting. To minimize the potential tumor cell contamination, PBPC harvests were scheduled at the end of HDS pretransplant phase. All patients had advanced-stage disease and most of them presented with bone marrow (BM) involvement. A tumor marker could be generated in 90% of patients using bcl-2 or Ig heavy-chain genes. MRD was analyzed on PBPC, BM harvests, and after autografting by polymerase chain reaction (PCR). All evaluable follicular and 6 of 9 mantle cell patients achieved clinical complete remission. PCR negativity of PBPC and/or BM harvests was documented in 68% of follicular and 12% of mantle cell lymphomas. Molecular remission of PBPC and/or BM harvests was achieved in 9 of 15 patients with overt marrow involvement and in all patients with only molecular marrow infiltration at onset. Molecular follow-up was conducted on 14 patients: all 7 evaluable patients who received at least one PCR-negative graft maintained the negative status at a median follow-up of 24 months and none of them relapsed so far. Thus, the results show that (1) a molecular marker to monitor MRD can be obtained in most follicular and mantle cell NHL patients, (2) the HDS regimen may provide PCR-negative PBPC and/or BM harvests even from patients with BM disease, and (3) autograft with at least one PCR-negative harvest is associated with a durable clinical and molecular remission.

No abstract

The feasibility and efficacy of a novel immunomagnetic ex vivo negative purging 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 study 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 then positive cell removal by passage on a Max-Sep (Baxter Immunotherapy) cell separator. Engraftment was rapid and stable. Hematological values were assessed 1 and 2 years after the autograft. Purging efficacy was molecularly assessed in a panel of 11 patients who showed persistence of PCR-detectable lymphoma cells on PBPC harvests despite intensified chemotherapeutic debulking. PCR-negativity was obtained in vitro and persisted in vivo after autograft in three FL patients; five more FL patients, whose purged PBPC were PCR+, converted to stable (3 patients) or fluctuating (two patients) PCR negativity after autograft. MCL patients never reached PCR negativity. Thus, ex vivo purging may have a role for FL patients harvesting PCR-positive PBPC after intensified chemotherapy. In contrast, the addition of ex vivo purging seems to be of little if any benefit for MCL patients.

An in vivo purging with intensive debulking chemotherapy prior to peripheral blood progenitor cell (PBPC) collection may reduce the risk of tumor contamination of the harvest products; however, it is usually associated with a marked reduction in PBPC mobilization. These issues have been considered while designing an adapted version of the high-dose sequential regimen for patients with lymphoid malignancies and bone marrow involvement. To reduce tumor contamination risks, PBPC collection was postponed to the end of the high-dose phase; however, in order to enhance progenitor cell mobilization, a chemotherapy-free lag period was introduced prior to the final mobilizing course. Thirty-nine patients (median age 47 years, range 26-62) with previously untreated indolent lymphoma entered this pilot study; all had advanced-stage disease, and 29 had overt marrow involvement. Sufficient numbers of PBPC to perform autograft with safety were harvested in 34 patients, with a median of 3 (range 2-5) leukaphereses. A median of 14.8 × 10 6 (range 2-51) CD34 + /kg and 32.6 × 10 4 (range 1.77-250) colony forming units-granulocyte/macrophage/kg were collected per patient. In univariate analysis, the duration of the chemotherapy-free interval prior to the final mobilizing course, i.e. > or <65 days, was the most significant variable influencing progenitor mobilization. These data suggest that extensive in vivo tumor debulking is feasible provided that a sufficient chemotherapy-free period preceding the mobilizing course is allowed in order to allow a full recovery of marrow functions.

Haemopoietic growth factor administration following high-dose chemotherapy markedly amplifies progenitor cell pool in the peripheral blood (PB). Collection and reinfusion of these cells enable rapid haemopoietic reconstitution following autograft. Less is known on engraftment potentiality of bone marrow (BM) cells taken under analogous conditions. To investigate this tissue, PB and BM were evaluated simultaneously during maximal mobilization in a series of 14 patients undergoing the HDS chemotherapy programme. A significantly higher growth of committed progenitors was found from PB rather than from BM (663 +/- 123 v 267 +/- 40 CFU-GM/10(5) MNC, respectively). Also, significantly more CFU-GM could be collected by a median of three leukaphereses, compared to those harvested from BM (158 +/- 31 v 16 +/- 4 x 10(4) CFU-GM/kg, respectively). Most mobilized CFU-GM were phenotypically immature (CD15-); in addition, circulating cells included primitive progenitors, as assessed by LTC-IC assay, or by evaluation of non-proliferating pre-CFU-GM, selected by an anti-CD71 immunotoxin. The amount of pre-CFU-GM determined by both techniques was consistently higher in PB than in BM. Moreover, a direct correlation could be established between circulating CFU-GM and primitive precursors. Thus, during optimally induced mobilization, PB contains many more haemopoietic progenitors, of both committed and primitive stages, than does BM. Under such conditions, PB is probably the best source of material for graft purposes.