Clinical and molecular remission after allogeneic blood cell transplantation in a patient with mantle-cell lymphoma

Current Approaches to Mantle Cell Lymphoma: Diagnosis, Prognosis, and Therapies

Mantle cell lymphoma (MCL) is a unique lymphoma subtype, both biologically and clinically. Virtually all cases are characterized by a common genetic lesion, t(11;14), resulting in overexpression of cyclin D1. The clinical course is moderately aggressive, and the disease is considered incurable. Considerable biologic and clinical heterogeneity exists, with some patients experiencing a rapidly progressive course, while others have disease that is readily managed. New tools exist for risk stratification and may allow for a more personalized approach in the future. Landmark studies have been completed in recent years and outcomes appear to be improving. Randomized clinical trials have clarified the role of high-dose cytarabine (Ara-C) for younger patients and have demonstrated a role for maintenance rituximab therapy. Multiple areas of uncertainty remain, however, and are the focus of ongoing research. This review focuses on (1) strategies to differentiate between aggressive and less aggressive cases, (2) understanding who should receive hematopoietic stem cell transplantation, and (3) the role for maintenance therapy in MCL.

Role of allogeneic stem cell transplantation in mantle cell lymphoma

Despite a wide spectrum of treatment options, mantle cell lymphoma (MCL) remains a challenging hematologic malignancy to manage. Advances in front-line therapy, including the monoclonal antibody rituximab and increasing use of cytarabine, have improved remission rates. Autologous hematopoietic cell transplantation (HCT) can effectively consolidate remission of MCL, leading to encouraging survival beyond 5 yr. However, nearly all patients with MCL will relapse and require salvage therapy. Novel agents such as ibrutinib, bortezomib, and lenalidomide have dramatically expanded the options for treating relapsed MCL. In this review, we summarize the clinical evidence supporting the use of allogeneic donor HCT in MCL and make recommendations on indications for its use. Data suggest that allogeneic donor HCT is the only curative therapy for patients with poor prognosis or aggressive MCL. Patient selection, timing, and optimal use remain a matter of scientific debate and given the rapidly changing therapeutic landscape of MCL, the outcomes of allogeneic HCT should be interpreted in the context of novel therapeutics.

Molecular remission is an independent predictor of clinical outcome in patients with mantle cell lymphoma after combined immunochemotherapy: a European MCL intergroup study

The prognostic impact of minimal residual disease (MRD) was analyzed in 259 patients with mantle cell lymphoma (MCL) treated within 2 randomized trials of the European MCL Network (MCL Younger and MCL Elderly trial). After rituximab-based induction treatment, 106 of 190 evaluable patients (56%) achieved a molecular remission (MR) based on blood and/or bone marrow (BM) analysis. MR resulted in a significantly improved response duration (RD; 87% vs 61% patients in remission at 2 years, P = .004) and emerged to be an independent prognostic factor for RD (hazard ratio = 0.4, 95% confidence interval, 0.1-0.9, P = .028). MR was highly predictive for prolonged RD independent of clinical response (complete response [CR], complete response unconfirmed [CRu], partial response [PR]; RD at 2 years: 94% in BM MRD-negative CR/CRu and 100% in BM MRD-negative PR, compared with 71% in BM MRD-positive CR/CRu and 51% in BM MRD-positive PR, P = .002). Sustained MR during the postinduction period was predictive for outcome in MCL Younger after autologous stem cell transplantation (ASCT; RD at 2 years 100% vs 65%, P = .001) and during maintenance in MCL Elderly (RD at 2 years: 76% vs 36%, P = .015). ASCT increased the proportion of patients in MR from 55% before high-dose therapy to 72% thereafter. Sequential MRD monitoring is a powerful predictor for treatment outcome in MCL. These trials are registered at www.clinicaltrials.gov as #NCT00209222 and #NCT00209209.

Rituximab Induces Effective Clearance of Minimal Residual Disease in Molecular Relapses of Mantle Cell Lymphoma

Molecular remission (MR) is associated with improved outcome in mantle cell lymphoma (MCL). If MR is not achieved, patients are at high risk of relapse. We retrospectively describe the molecular and clinical follow-ups of 4 patients with molecular relapses (M-rels) who were treated with rituximab. The 4 patients received rituximab-supplemented, high-dose sequential chemotherapy and autologous stem cell transplantation as induction treatment and achieved clinical remission and MR. M-rel was defined as polymerase chain reaction (PCR) positivity in 2 consecutive samples in the absence of clinical relapse. M-rels occurred at 3, 6, 39, and 52 months and were always confirmed by direct sequencing of the clonal rearrangement. Minimal residual disease was monitored by qualitative and real-time quantitative PCR. All patients received 4 courses of rituximab, with 2 additional infusions if PCR positivity remained. After 4-6 courses of rituximab, all patients re-entered MR. No clinical relapses were recorded at 3, 6, 18, and 62 months from treatment, although 1 patient had a second M-rel that was sensitive to rituximab. Our results indicate that rituximab is active against residual MCL cells and suggest that molecularly tailored maintenance therapy needs to be investigated in clinical trials.

The graft-versus-lymphoma effect: clinical review and future opportunities

Numerous lines of preclinical and clinical evidence support the existence of a graft-versus-leukemia effect, but less evidence supporting a comparable graft-versus-lymphoma effect exists. We review here current clinical data addressing the graft-versus-lymphoma effect, including comparisons of autologous, syngeneic, and allogeneic transplantation; responses to immunomodulation; and responses to nonmyeloablative stem cell transplantation. Despite several limitations of the data, we believe that there is sufficient evidence suggesting a significant graft-versus-lymphoma effect. In addition, we discuss approaches for clinical management of lymphoma patients, opportunities for mechanistic studies afforded by donor leukocyte infusions and nonmyeloablative transplantation, and suggestions for clinical studies to further define the magnitude and applicability of the graft-versus-lymphoma effect.

The role of allogeneic transplantation in non-Hodgkin's lymphoma

The evolution of combination chemotherapy regimens, combined with improvements in supportive care, has incrementally improved survival outcomes for patients with non-Hodgkin's lymphomas (NHL). Although 40-60% of younger patients with diffuse large cell lymphoma can now expect to be cured, significant numbers will either fail to achieve a remission or relapse after attaining a remission. In addition, certain histological subtypes are associated with particularly poor prognoses with combination chemotherapy alone (e.g. mantle cell lymphoma, B-cell prolymphocytic leukaemia). Relatively few of these patients can achieve long-term responses. Other NHL subtypes, whilst associated with more favourable prognoses in terms of overall survival, are rarely, if ever, cured (e.g. most low grade NHL including follicular lymphoma, chronic lymphocytic leukaemia and small lymphocytic lymphoma). For these reasons dose escalation and allogeneic transplantation have been investigated as potential ways of improving outcome, although this has mainly been in the setting of advanced disease. Any possible benefits have frequently been out-weighed by procedural morbidity and mortality. The parallel development of transplantation approaches that limit procedural toxicity along with advances in supportive care require that the role of allogeneic haematopoietic stem cell transplantation in the management of lymphoma be re-evaluated.

Autologous and allogeneic transplantation for aggressive NHL

BACKGROUND

Intermediate- and high-grade NHL are generally chemosensitive diseases with high initial response rates to combination chemotherapy. Dose intensification via autologous and allogeneic transplantation provides viable treatment options in specific clinical settings. Currently, autologous transplantation is the standard of care for relapsed but chemosensitive aggressive B-cell NHL. However, tools such as the International Prognostic Index allow risk-adapted analyses, and show that the magnitude of benefit from autologous transplantation differs in lymphoma subsets.

METHODS

Low-risk patients appear to do well regardless of salvage approaches, whereas high-risk patients have suboptimal outcomes with autologous transplantation. In high-risk patients, high-dose chemotherapy with autologous stem-cell transplantation has been examined as part of initial therapy, with long-term data promising but still evolving.

DISCUSSION

A significant concern with autologous transplantation in aggressive and high-grade NHL is the risk of graft contamination with tumor cells. Several investigators have demonstrated the presence of malignant cells in both BM and PBSC, although the clonagenic potential of such cells is unclear. Allogeneic stem-cell transplantation has several potential advantages over autologous transplantation for NHL,including procurement of an uncontaminated stem-cell graft, GvL effects, and the elimination of hematopoietic stem-cell damage and consequent secondary leukemia.

RESULTS

The ideal application of allogeneic transplantation in aggressive and high-grade lymphomas is still unclear; but the lower relapse rates demonstrated in several comparisons of the two approaches make this an exciting area to pursue. Finally, non-myeloablative stem-cell transplantation may broaden the use of allogeneic transplantation by lowering regimen-related mortality while capitalizing on GvL.

The choice of allogeneic or autologous hematopoietic transplantation for NHL

NHL constitutes the sixth most common malignancy diagnosed in the USA every year, accounting for approximately 24,400 deaths. Although a subset of patients can be cured with chemotherapy or radiation therapy, the outlook is generally poor for patients with refractory or recurrent disease. High-dose therapy supported by both autologous and allogeneic transplantation has been widely studied in this group of patients. Autologous transplantation may be considered standard therapy for patients with diffuse large-cell NHL in chemotherapy-sensitive relapse. Selected categories of patients with other histologic subtypes may also benefit from this strategy. Allogeneic transplantation using high-dose myeloablative conditioning regimen is an effective, yet hazardous approach. A GvL effect leads to a lower rate of disease recurrence than occurs with autologous transplants, but this benefit is offset by higher risk of treatment related mortality. The recent use of less toxic non-myeloablative conditioning regimens for allogeneic transplantation has reduced the risk of transplant-related mortality, allowing this approach even in older or medically infirm patients. Nonablative allogeneic transplants are a promising strategy, particularly for patients with indolent lymphoid malignancies.

Outcome of autologous transplantation for mantle cell lymphoma: a study by the European Blood and Bone Marrow Transplant and Autologous Blood and Marrow Transplant Registries

Mantle cell lymphoma (MCL) has an aggressive clinical course with a median survival < 3 years and is incurable with conventional chemotherapy. A large multicentre study with adequate follow-up may clarify the role of significant factors affecting outcome in autologous stem cell transplantation for MCL. Patients receiving an autologous transplant for MCL between 1988 and 1998, and reported to the European Blood and bone Marrow Transplant (EBMT) registry or Autologous Blood and Marrow Transplant Registry (ABMTR), were included. Expert haematopathology review was required on all identified patients. Disease and transplant details were requested from the transplant centres, and the final cohort of patients with verified pathology, adequate clinical information and follow-up was analysed. One hundred and ninety-five patients were included in the analyses (149 EBMT, 46 ABMTR) with a median follow-up of 3.9 years. The 2 year and 5 year overall survival were 76% and 50%, and progression free survival was 55% and 33% respectively. Disease status at transplant was the most significant factor affecting survival: patients with chemosensitive disease but not in first complete remission (CR1) were 2.99 times (95% CI: 1.66-5.38, P < 0.001) more likely to die than patients transplanted in CR1. Autologous transplantation probably improves survival in patients with MCL especially if performed in first CR.

Detection of minimal residual disease

A high percentage of patients with leukemia, lymphoma, and solid tumors achieve a complete clinical remission after initial treatment, but the majority of these patients will finally relapse from residual tumor cells detectable in clinical remission only by the most sensitive methods. The in vitro amplification of tumor-specific DNA or RNA sequences by polymerase chain reaction (PCR) allows identification of a few neoplastic cells in 10(4) to 10(6) normal cells. Depending on the underlying malignant disease and therapeutic treatment, the presence of residual tumor cells in an individual patient may herald relapse, but a long-term stable situation or slowly vanishing tumor cells are also possible. Molecular monitoring of residual leukemia and lymphoma cells by quantitative PCR techniques has provided important information about the effectiveness of treatment and the risk of recurrent disease as shown by minimal residual disease (MRD) analysis in patients with various malignant diseases. Such diseases include childhood acute lymphoblastic leukemia, after induction therapy; acute promyelocytic leukemia, during and after chemotherapy; and chronic myelogenous leukemia, during treatment with alpha-interferon and after allogeneic bone marrow transplantation. Evaluation of the predictive value of the detection of MRD has to take into account its evolution and course, the pathogenesis, biology, and natural course of the underlying malignant disease, the molecular genetic lesion, and finally, the type of treatment. Quantification of minimal residual cells by the recently developed real-time quantitative PCR technique will surely have a major impact on our therapeutic strategies for patients with leukemia, lymphomas, and solid tumors. Based on quantitative PCR data, the terms molecular remission and molecular relapse have to be exactly defined and validated in prospective clinical trials to assess the biological and clinical significance of MRD in various types of malignancies.

Stem cell transplantation for mantle cell lymphoma: should it ever be used outside clinical trials?

The outlook for patients with mantle cell lymphoma is poor. The reported median survival in most published series is only 3 to 4 years, and even the most favorable prognostic groups have median survival rates of only 5 years, with no evidence of cure. The use of autologous and allogeneic stem cell transplantation in this disease has increased dramatically in recent years. Despite encouraging reports from single centers and registries, the impact of stem cell transplantation on the outcome for mantle cell lymphoma is unclear. Optimal first-line regimens for mantle cell lymphoma have yet to be defined, and it is therefore difficult to place the role of first remission transplantation in an appropriate context. Prospective randomized trials have been difficult to design and conduct in the absence of a well-defined 'standard' treatment. The role of stem cell transplantation as a salvage strategy is also unknown, although available data suggest that it does not improve survival in heavily pre-treated patients. In the absence of clear evidence for a survival advantage for patients receiving stem cell transplants for mantle cell lymphoma, entry into clinical trials should be a priority.

Peripheral blood stem cells for allogeneic transplantation: a review

Peripheral blood stem cells (PBSCs) have become increasingly popular for use in hematopoietic stem cell transplantation. PBSCs are readily collected by continuous-flow apheresis from patients and healthy donors after the administration of s.c. recombinant colony-stimulating factors with only minimal morbidity and discomfort. Although the precise identification of PBSCs remains elusive, they can be phenotypically identified as a subset of all circulating CD34(+) cells. There are important phenotypic and biologic distinctions between PBSCs and bone marrow (BM)-derived progenitor cells. PBSCs express more lineage-specific antigens but are less metabolically active than their BM-derived counterparts. The use of PBSCs for allogeneic transplantation has been compared to BM in several randomized trials and cohort studies. The use of PBSCs in leukemia, myeloma, non-Hodgkin's lymphoma, and myelodysplasia has resulted in shorter times to neutrophil and platelet engraftment at the expense of increased rates of chronic graft-versus-host disease. The increase in graft-versus-host disease is mainly due to a log-fold increase in donor T cells transferred with the graft. Relapse rates after transplantation may be lower after PBSC transplantation but a convincing survival advantage has not been demonstrated overall. It is possible that a stronger graft-versus-tumor effect may exist with PBSCs when compared with BM although the mechanisms leading to this effect are not clear.

Long-term clinical and molecular remission after allogeneic stem cell transplantation (SCT) in patients with poor prognosis non-Hodgkin's lymphoma

From 1987 to 1999 35 patients with poor prognosis non-Hodgkin's lymphoma (NHL) underwent allogeneic stem cell transplantation (SCT) at the University Hospitals of Vienna and Graz. Initial biopsy specimens were reclassified according to the Revised European-American Classification of Lymphoid Neoplasms (REAL). All patients surviving 28 days engrafted. Twenty-eight of them (93%) attained clinical remission. At the last follow-up 14 patients were alive and disease-free at a median of 5.0 (range, 2.3-12.9) years after allogeneic SCT. The actuarial overall survival is 35%. Five patients relapsed 1.8 to 27.6 months after transplant, the probability of relapse is 23%. Of the 21 deaths following SCT, seven were due to relapse/refractory disease and 14 due to transplant-related causes. The probability of treatment-related mortality is 48%. After SCT, minimal residual disease (MRD) was monitored by polymerase chain reaction (PCR) in seven patients with a BCL-2/IgH translocation and in 13 with a clonal immunoglobulin heavy chain (IgH) rearrangement. All 20 patients attained clinical remission rapidly and converted to PCR negativity. In the follow-up nine of these patients are in long-term clinical and molecular remission, six PCR-negative patients died of transplant-related causes and five patients relapsed. In summary, allogeneic stem cell transplantation has a curative potential for patients with refractory and recurrent non-Hodgkin's lymphoma. In our series long-term disease-free survival was associated with molecular disease eradication after SCT. Treatment-related mortality rate was high, thus earlier referral of selected patients to allogeneic SCT should be considered.

Central nervous system relapse in a patient with mantle cell lymphoma in continuous clinical and molecular remission at six years since autografting

Although molecular remissions have been frequently observed and associated with low likelihood of relapse in some lymphoid tumours, they are seldom reported in mantle cell lymphoma (MCL). We performed PCR analysis of a MCL patient with central nervous system (CNS) relapse occurring 76 months after autologous transplantation. Molecular follow-up showed constant absence of PCR-detectable disease, even after the onset of relapse. These data indicate that isolated CNS relapse may occur even after several years of continuous remission and cannot be excluded based on a persistent pattern of molecular remission. However, the prolonged remission duration observed in this patient suggests that achieving PCR-negativity may also be of benefit for MCL patients.

Allogeneic stem cell transplantation for the non-Hodgkin's lymphomas and Hodgkin's disease

Certain poor-prognosis patients with non-Hodgkin's lymphoma and Hodgkin's disease, usually with recurrent and/or refractory disease, are rarely curable with standard chemoradiotherapy. Autologous hematopoietic stem cell transplantation has been shown to result in improved long-term disease-free survival in some of these patients. Unfortunately, a number of patients are not suitable for autologous transplantation due to a damaged stem cell pool involvement or other disease processes of the marrow. These patients may benefit from allogeneic stem cell transplantation. In addition to the therapeutic effect of high-dose chemotherapy with or without total body irradiation, an immunologic [i.e. graft-versus-lymphoma (GVLym)] effect may be present in some patients undergoing allogeneic transplantation, resulting in a lower relapse rate than autotransplants. However, allografts are almost always associated with a higher non-relapse mortality due primarily to graft-versus-host disease (GVHD); unfortunately, GVHD and GVLym are difficult to separate. Thus, full exploitation of this GVLym effect may require the modification of commonly used conditioning regimens; if successful, these modifications may allow an additional decrement in the incidence of relapse without additional morbidity. Also, when combined with lesser intensity conditioning, such may permit patients who otherwise would not be candidates for standard transplant regimens to be allografted.

Patients with mantle-cell lymphoma relapsing after autologous stem cell transplantation may be rescued by allogeneic transplantation

Two patients with disseminated mantle-cell lymphoma relapsed 24 and 13 months, respectively, after high-dose chemotherapy and autologous stem cell transplantation (autoSCT). Both patients had an HLA-identical sibling and received an allogeneic stem cell transplant (alloSCT) 32 and 18 months after autologous transplant, after conditioning with fractionated 12 Gy total body irradiation plus cyclophosphamide 120 mg/kg. They are both alive and in complete remission 24 months after transplant. Both patients have developed chronic graft-versus-host disease and their Karnofsky performance status is 90%. AlloSCT may offer a useful approach in a subgroup of patients with mantle-cell lymphoma who have relapsed after autologous transplantation.

Successful allogeneic stem-cell transplantation with prophylactic stepwise G-CSF primed-DLIs for relapse after autologous transplantation in mantle cell lymphoma: a case report and literature review on the evidence of GVL effects in MCL

Mantle cell lymphoma (MCL) is a distinctive clinicopathologic entity and represents 2-8% of all non-Hodgkin's lymphomas. The median survival of patients with MCL is only 3 years, and none of the available conventional chemotherapy regimens appears curative. Encouraging results have been reported with high-dose chemotherapy with autologous stem-cell transplantation (autoSCT). However, a plateau in disease-free survival was not observed in relapsed MCL on the autoSCT trials. Promisingly, alloSCT appears to induce durable remissions via a graft-versus-lymphoma (GVL) effect. Donor lymphocyte infusions (DLIs), by virtue of a GVL effect, have been shown to induce durable remissions in a few cases with refractory MCL that recur after alloSCT. In this article, we review the literature on the evidence of the GVL effects in MCL and describe a patient with relapsed MCL shortly after high-dose chemotherapy with autoSCT. The patient was then successfully treated with Bu/Cy/VP-16 for an alloSCT followed by DLIs in a stepwise fashion. MNCs > 10 x 10(8)/kg were collected by two large-volume leukaphereses from the donor. Harvested stem cells from the 2(nd) day were cryopreserved for the future use as prophylactic DLIs to be given in a stepwise fashion. Cyclosporin and methotrexate were used for GVHD prophylaxis. He had achieved only a partial response by D+64 post transplant. G-CSF-primed cryopreserved DLIs were then infused on D+64 and D+92 to enhance the GVL effect. Grade 3 intestinal GVHD developed 20 days after the 2(nd) DLI and was partially controlled with the combination of cyclosporin, prednisone, and mycophenolate mofetil. Clinical complete remission was observed at D+112, and maintained until the last follow-up day (D+615). Our findings suggest that alloSCT followed by prophylactic DLIs may offer a curative approach to refractory MCL.

Mantle cell lymphoma. A clinicopathologic study of 68 cases from the Nebraska Lymphoma Study Group

Although mantle cell lymphoma (MCL) is considered a distinctive disease entity within non-Hodgkin's lymphoma (NHL), the cytology and growth pattern of MCL can be quite variable and the clinical significance of these features is unclear. Also, the role of anthracyclines in the management of MCL is unclear. Therefore, we examined our experience with MCL in an effort to clarify these important issues. We identified 68 patients with MCL who were evaluated clinically and treated by the Nebraska Lymphoma Study Group. Treatment consisted of combination chemotherapy containing an anthracycline in 76% of the patients. The cases were grouped by blastic or lymphocytic cytology, and the latter were divided by growth pattern into nodular (or mantle-zone) and diffuse types. The clinical and pathological variables were then evaluated for their prognostic value. The median overall survival (OS) and failure-free survival (FFS) for the entire group were 38 months and 12 months, respectively, and there was no survival advantage for those who received an anthracycline. The cases were grouped as follows: blastic type, 26%; nodular lymphocytic type, 44%; and diffuse lymphocytic type, 30%. Both the cytology and pattern of growth were predictive of OS and FFS. The median OS was as follows: blastic type, 55 months; nodular lymphocytic type, 50 months; and diffuse lymphocytic type, 16 months (P = 0.0038). The clinical features that predicted for a shorter survival included bone marrow involvement, advanced stage disease, B symptoms, a poor performance score, and the International Prognostic Index. We conclude that new therapeutic approaches, with the patients stratified by histologic type and clinical prognostic factors, are clearly needed for MCL.

Allogeneic bone marrow transplantation for lymphoma

Registry data show that use of allogeneic transplantation for non-Hodgkin's lymphoma, and to a lesser extent, Hodgkin's disease is increasing. Although no prospective randomized trials have been performed, most comparisons show a significantly lower relapse rate when allogeneic transplant results are compared to results of autologous hematopoietic stem cell transplantation. The lower relapse rate following allogeneic transplantation, as well as several other lines of evidence, support the existence of a graft-versus-lymphoma effect. Nevertheless, in most comparisons, the lower relapse rate following allogeneic transplantation is offset by higher transplant-related mortality. These results make it difficult to find situations where definite overall survival advantages associated with the use of allogeneic transplantation can be demonstrated. The use of low-intensity non-myeloablative regimens for allogeneic transplantation is attracting attention. It is hoped that this approach may harness a graft-versus-lymphoma effect with less morbidity and mortality than conventional allogeneic transplantation, but more data are required to assess the value of this treatment.

Allogeneic hematopoietic transplantation for chronic lymphocytic leukemia and lymphoma: potential for nonablative preparative regimens

There is increasing interest in the use of allogeneic blood and marrow transplants for chronic lymphocytic leukemia (CLL) and lymphomas. Numerous studies indicate efficacy in patients with advanced disease and demonstrate existence of a potent graft-versus-malignancy effect against these disorders. Allogeneic transplantation is most effective in CLL and low-grade lymphomas, but precise indications and timing of allogeneic transplants in these indolent disorders are not well defined. Allotransplantation is an effective, potentially curative approach, albeit with substantial risks; it is indicated in selected categories of patients. Allogeneic transplants are also promising for mantle cell lymphoma. In large-cell lymphoma, relapses are reduced in allogeneic compared with autologous transplants, but the benefit of allotransplantation has been offset by increased risk of treatment-related complications, and its indications are controversial. A promising new strategy is the use of less toxic, nonmyeloablative preparative regimens to achieve engraftment and allow development of graft-versus-malignancy effects that can produce durable remission in selected categories of lymphoid malignancies.

Failure of Immunologic Purging in Mantle Cell Lymphoma Assessed by Polymerase Chain Reaction Detection of Minimal Residual Disease

To assess the clinical significance of minimal residual disease (MRD) detection by polymerase chain reaction (PCR) we analyzed samples from 26 patients with mantle cell lymphoma (MCL) who had undergone bone marrow transplantation (BMT) at the Dana-Farber Cancer Institute. The BCL-1/IgH translocation and clonally rearranged Ig heavy chain genes (IgH) provided molecular markers for detection and follow-up of MRD by polymerase chain reaction (PCR) amplification in 19 of the 26 (73%) MCL patients studied. IgH gene sequencing analysis showed somatic mutations in MCL that are characteristic of an antigen driven process suggesting that, in MCL, the final malignant transformation occurs in a mature B cell. Of the 19 patients with a PCR amplifiable marker, 17 underwent autologous, 1 an allogeneic, and 1 a syngeneic bone marrow transplantation (BMT). All patients had PCR-detectable MRD in the bone marrow (BM) at the time of BMT, irrespective of any history of histological BM involvement. In contrast to other B-cell malignancies, we found that immunological purging with complement-mediated lysis eradicated PCR-detectable MCL in only two patients. Moreover reinfusion of MRD was associated with a poor outcome. More than half of the patients undergoing autologous BMT had relapsed by the time of restaging at 2 years after autologous BMT. In four MCL patients in whom no residual lymphoma was reinfused, including the allogeneic and the syngeneic BMT, only one patient relapsed. Persistence of MRD detection after BMT was also associated with a high probability of relapse, although one patient did not have PCR-detectable MRD in peripheral blood or BM before relapse at nodal sites. We conclude that PCR amplification of disease-specific markers is a feasible and sensitive method to assess MRD and its clinical significance in patients with MCL. Moreover, PCR amplification provides a tool to evaluate modifications of purging and stem cell collection procedures that may be required for the management of this otherwise incurable disease.