The remission status before and the PCR status after high-dose therapy with peripheral blood stem cell support are prognostic factors for relapse-free survival in patients with follicular non-Hodgkin's lymphoma

High-throughput sequencing for noninvasive disease detection in hematologic malignancies

Noninvasive monitoring of minimal residual disease (MRD) has led to significant advances in personalized management of patients with hematologic malignancies. Improved therapeutic options and prolonged survival have further increased the need for sensitive tumor assessment that can inform treatment decisions and patient outcomes. At diagnosis or relapse of most hematologic neoplasms, malignant cells are often easily accessible in the blood as circulating tumor cells (CTCs), making them ideal targets to noninvasively profile the molecular features of each patient. In other cancer types, CTCs are generally rare and noninvasive molecular detection relies on circulating tumor DNA (ctDNA) shed from tumor deposits into circulation. The ability to precisely detect and quantify CTCs and ctDNA could minimize invasive procedures and improve prediction of clinical outcomes. Technical advances in MRD detection methods in recent years have led to reduced costs and increased sensitivity, specificity, and applicability. Among currently available tests, high-throughput sequencing (HTS)-based approaches are increasingly attractive for noninvasive molecular testing. HTS-based methods can simultaneously identify multiple genetic markers with high sensitivity and specificity without individual optimization. In this review, we present an overview of techniques used for noninvasive molecular disease detection in selected myeloid and lymphoid neoplasms, with a focus on the current and future role of HTS-based assays.

Persistence of minimal residual disease in bone marrow predicts outcome in follicular lymphomas treated with a rituximab-intensive program

PCR negativity is a strong outcome predictor after rituximab-intensive immunochemotherapy at multiple posttreatment times. PCR is predictive even when maintenance is delivered, and accumulation of PCR-negative results further reduces the likelihood of relapse.

Clinical implications and prognostic role of minimal residual disease detection in follicular lymphoma

The identification of patients at high risk of relapse is a critical goal of modern translational research in oncohematology. Minimal residual disease (MRD) detection by polymerase chain reaction-based methods is routinely employed in the management of patients with acute lymphoblastic leukemia. Current knowledge indicates that it is also a useful prognostic tool in several mature lymphoproliferative disorders and particularly in follicular lymphoma (FL). Based on this evidence clinical trials employing MRD-based risk stratification are currently ongoing in FL. In this review the 'state of the art' of MRD evaluation in FL is discussed. A short description of technical issues and recent methodological advances is provided. Then, the bulk of the review focuses on critical take-home messages for clinicians working in the field. Finally, we discuss future perspectives of MRD detection and more generally outcome prediction in FL.

MRD detection in B-cell non-Hodgkin lymphomas using Ig gene rearrangements and chromosomal translocations as targets for real-time quantitative PCR

Minimal residual disease (MRD) diagnostics is of high clinical relevance in patients with indolent B-cell Non-Hodgkin lymphomas (B-NHL) and serves as a surrogate parameter to evaluate treatment effectiveness and long-term prognosis. MRD diagnostics performed by real-time quantitative PCR (RQ-PCR) is the gold-standard and currently the most sensitive and the most broadly applied method in follicular lymphoma (FL) and mantle cell lymphoma (MCL). RQ-PCR analysis of the junctional regions of the rearranged immunoglobulin heavy-chain gene (IgH) serves as the most broadly applicable MRD target in B-NHL (∼80%). Chromosomal translocations as t(14;18) translocation in FL and t(11;14) translocation in MCL can be used in selected lymphoma subtypes. In patients with B-cell chronic lymphocytic leukemia, both flow-cytometry as well as RQ-PCR are equally suitable for MRD assessment as long as a sensitivity of ≤10(-4) shall be achieved.MRD diagnostics targeting the IgH gene is complex and requires extensive knowledge and experience because the junctional regions of each lymphoma have to be identified before the patient-specific RQ-PCR assays can be designed for MRD monitoring. Furthermore, somatic mutations of the IgH region occurring during B-cell development of germinal center and post-germinal center lymphomas may hamper appropriate primer binding leading to false negative results. The translocations mentioned above have the advantage that consensus forward primers and probes, both placed in the breakpoint regions of chromosome 18 in FL and chromosome 11 in MCL, can be used in combination with a reverse primer placed in the IgH joining region of chromosome 14. RQ-PCR-based methods can reach a good sensitivity (≤10(-4)). This chapter provides all relevant background information and technical aspects for the complete laboratory process from detection of the clonal IgH gene rearrangement and the chromosomal translocations at diagnosis to the actual MRD measurements in clinical follow-up samples of B-NHL. However, it should be noted that MRD diagnostics for clinical treatment protocols has to be accompanied by regular international quality control rounds to ensure the reproducibility and reliability of the MRD results.

BCL-2/IgH polymerase chain reaction status at the end of induction treatment is not predictive for progression-free survival in relapsed/resistant follicular lymphoma: results of a prospective randomized EORTC 20981 phase III intergroup study

PURPOSE

The prognostic value of residual BCL2/immunoglobulin heavy chain (BCL2/IgH) -positive cells in peripheral blood (PB) or bone marrow (BM) after induction treatment in follicular lymphoma (FL) is still controversial. In a prospective randomized phase III intergroup trial of 465 patients with relapsed/resistant follicular lymphoma (FL), we showed that addition of rituximab to cyclophosphamide, doxorubicin, vincristine, and prednisone induction results in increased overall and complete response rates, and that rituximab maintenance strongly improves median progression-free survival (PFS) as well as overall survival. Here, we studied whether BCL2/IgH major break point levels in PB/BM correlated with response rates/quality for the induction phase and PFS for the maintenance phase.

PATIENTS AND METHODS

Samples were obtained before and after induction therapy and at the end of the 2 years maintenance/observation period. BCL2/IgH major break point-positive cells were quantified by genomic quantitative polymerase chain reaction in 792 samples from 238 patients.

RESULTS

Pretreatment BCL2/IgH levels had no significant prognostic value for overall response or complete remission rates after induction treatment, but pretreatment positive BM results had an adverse prognostic value for PFS from first randomization (P = .023). Importantly, BCL2/IgH levels at the end of induction treatment had no prognostic value for PFS from second randomization. The highly significant improved PFS by rituximab maintenance was observed in both BCL2/IgH PB/BM-positive and -negative groups.

CONCLUSION

Postinduction BCL2/IgH major break point status in BM/PB is not useful for decisions on subsequent therapy for patients with relapsed/resistant FL.

Rituximab purging and maintenance combined with auto-SCT: long-term molecular remissions and prolonged hypogammaglobulinemia in relapsed follicular lymphoma

We enrolled 23 patients with relapsed follicular lymphoma (FL) in a prospective single-arm study of auto-SCT combined with in vivo rituximab graft purging and post transplant rituximab maintenance. Minimal residual disease was monitored with quantitative PCR testing. With a median follow-up of 74.2 months, neither median overall survival (OS) nor PFS has been reached. Here, 5-year OS and 5-year PFS are 78% (95% confidence interval (CI) 61-95%) and 59% (95% CI 38-80%), respectively. Time to progression (TTP) with the experimental regimen was significantly improved compared with TTP with the last prior treatment (P<0.001). Durable molecular remissions occurred in 11 of 13 assessable patients. PFS was significantly longer in patients who achieved a molecular remission by 3 months post-auto-SCT (P=0.001). Prolonged hypogammaglobulinemia occurred in most patients; however, no increase in major infections was observed.

Commercial LightCycler-based quantitative real-time PCR compared to nested PCR for monitoring of Bcl-2/IgH rearrangement in patients with follicular lymphoma

Translocation of chromosomes 14 and 18 [t(14;18)] for detection of minimal residual disease in follicular lymphoma patients can be analyzed by nested polymerase chain reaction (PCR) or by quantitative PCR like LightCycler-based assays. We have compared both methods in blood and bone marrow samples of 28 patients enrolled in a clinical study on immunochemotherapy. In 42% of samples, the bcl2-IgH rearrangement was detectable by nested PCR, but not by LightCycler PCR. Nested PCR was able to reveal a significant drop in positive bone marrow or peripheral blood samples after therapy. In contrast, with LightCycler PCR, the detected drop in t(14;18)-positive cells did not reach statistical significance. The majority of patients showed positive results with nested PCR of peripheral blood or bone marrow without any associations to presence or absence of histological bone marrow (BM) infiltration by lymphoma cells. With LightCycler PCR, the numbers of positive cells were higher in samples from patients with BM infiltration of lymphoma cells (1.9 x 10(-2)) compared to samples from patients without involvement (4.08 x 10(-5)). A similar trend was seen in samples derived from the peripheral blood. Positivity for t(14;18) after therapy in two patients correlated with clinical relapse 6 months later. The data shown here demonstrate a lower sensitivity of LightCycler vs. nested PCR for detection of t(14;18). The usefulness of nested PCR for t(14;18) for risk stratification after primary therapy has to be validated in larger trials.

Molecular methods used for the detection of autologous graft contamination in lymphoid disorders

Intensified treatments aimed at maximal tumor reduction are an important therapeutic option for patients affected by B-cell malignancies. The possibility of obtaining a relevant number of clinical complete remissions after these treatments prompted the application of molecular techniques for the detection of extremely low numbers of residual malignant cells. These cells can be present either in the stem cell graft or, during the follow-up, in the bone marrow of patients attaining a clinical complete remission. The most sensitive and widely used techniques for minimal residual disease (MRD) assessment are those based on the PCR method. These methods allow the detection of autologous graft contamination and the identification of patients at high risk of disease recurrence by means of post-transplant MRD monitoring. In this setting, quantitative PCR assays can evaluate the kinetics of tumor clone growth in complete remission (CR) patients showing a persistence of PCR detectable tumor cells with standard qualitative methods.

Prolonged survival and low incidence of late toxic sequelae in advanced follicular lymphoma treated with a TBI-free autografting program: updated results of the multicenter consecutive GITMO trial

This study provides an updated report of the consecutive multicenter Gruppo Italiano Trapianto Midollo Osseo trial employing an intensified, purging-free, total body irradiation-free, high-dose sequential chemotherapy schedule with peripheral blood stem cell autograft (i-HDS) in advanced-stage follicular lymphoma (FL). Special interest has been devoted to late toxicities and outcome in terms of molecular status. Ninety-two untreated FL patients aged <or=60 were enrolled by 20 Italian centers and evaluated on an intention-to-treat basis. Main findings are as follows: (1) 5.5-years overall survival projection of 80% (median follow-up: 68 months), with no differences related to age-adjusted IPI score; (2) 46 (50%) of 92 patients presently in continuous complete remission; (3) projected long-term progression-free survival exceeding 80% for patients collecting PCR-negative stem cell harvests or achieving molecular remission within the first 2 years from the end of therapy; (4) actuarial 5-years risk of developing secondary myelodysplasia and acute myeloid leukemia of 3.7%, with most of these events occurring in patients re-treated for recurrent lymphoma. These results demonstrate that i-HDS is feasible, effective and safe even in terms of long-term outcome. As the HDS schedule can be easily supplemented with Rituximab, it is one of the best options for random comparison with Rituximab-supplemented conventional chemotherapy.

The role of hematopoietic cell transplantation for follicular non-Hodgkin's lymphoma

The overall survival with follicular lymphoma has not significantly changed over the last few decades, and there is no universal agreement as to the optimal first-line or subsequent therapy. High-dose chemotherapy with autologous hematopoietic cell transplantation (HCT) confers high response rates and improved progression-free survival in advanced-stage disease, and more recent data indicate a positive effect on overall survival. Initial results with myeloablative allogeneic HCT unequivocally demonstrated a reduction in relapse/progression compared with autologous HCT, but it is associated with prohibitive nonrelapse mortality. Nonmyeloablative or reduced-intensity regimens have substantially reduced up-front toxicity, and preliminary data seem highly encouraging with regard to efficacy. Novel strategies include the use of rituximab for in vivo purging and maintenance therapy. The incorporation of radioimmunoconjugates into conditioning regimens to deliver targeted radiotherapy also appears promising. This review summarizes current and new developments regarding the role of HCT for patients with follicular lymphoma.

The significance of minimal residual disease in stem cell grafts and the role of purging: is it better to purge in vivo or in vitro?

Contamination of autologous graft by tumor, in addition to incomplete tumor eradication, can partly explain why relapse remains the commonest cause of treatment failure after autologous stem cell transplantation (ASCT) in patients with malignant hematologic disorders. Monitoring of minimal residual disease (MRD) is now recognized as an important diagnostic tool for assessment either of the response to treatments aimed at maximal cytoreduction and the individual risk of relapse. In order to improve cure rates, many strategies to achieve in vivo or in vitro reduction, if not eradication, of residual disease have been proposed. We discuss the significance of MRD and the role of purging in the ASCT setting, focusing on acute myeloid leukemia, chronic myeloid leukemia, multiple myeloma and follicular lymphoma.

Detection and monitoring of minimal residual disease by quantitative real-time PCR

BACKGROUND

The detection of malignant cells by quantitative real-time PCR has become state of the art for diagnosis, monitoring response to treatment and detection of minimal residual disease (MRD) in patients with leukemia or lymphoma. In order to be used in high-throughput analyses technical details have to be standardized to improve reproducibility and comparability of quantitative results obtained in different laboratories.

METHODS

Molecular monitoring of disease activity during and after treatment based on the detection of malignant cells in circulation or bone marrow by quantitative real-time PCR will be helpful to develop individualized treatment strategies for every patient.

CONCLUSIONS

The effectiveness of any kind of innovative treatment with specific antibodies, cellular immunotherapy or molecules designed for specific targets of tumor cells can be controlled at a very high level of sensitivity and accuracy. Based on quantitative results indicative for success or treatment failure, therapeutic changes upon the detection of progressive disease at the molecular level can be made even before symptoms or signs of clinical relapse occur. Hopefully, this will lead to higher cure rates and improved long-term survival.

LightCyclerR-based quantitative real-time PCR monitoring of patients with follicular lymphoma receiving rituximab in combination with conventional or high-dose cytotoxic chemotherapy

OBJECTIVES

Quantitative real-time polymerase chain reaction (qPCR) is a suitable method to measure residual disease in hematological malignancies. Our objective was to assess a LightCycler-based qPCR for t(14;18)(q32;q21)(IgH/bcl-2)-positive cells quantification in the context of clinical and morphopathological characteristics of patients with follicular lymphoma treated with rituximab (R) in combination with conventional or high-dose chemotherapy.

METHODS

A total of 270 bone marrow (BM) and peripheral blood (PB) samples collected from 52 patients with follicular lymphoma at diagnosis or at relapse before or sequentially during therapy were examined by qPCR and nested-PCR.

RESULTS

A greater amount of t(14;18)-positive cells was observed in BM in comparison with PB in 76% of paired samples. The presence and number of t(14;18)-positive cells in BM and PB correlated with lymphoma activity. Significantly higher numbers of lymphoma cells were found in patients under non-remission compared with patients in clinical remission. During non-remission, 10-fold higher numbers were measured at relapse than at diagnosis. During remission, significantly higher levels were found in partial compared with complete remission. During first-line therapy, R/cyclophosphamide/adriamycin/vincristine/prednisone (CHOP) had higher in vivo purging ability than R/fludarabine/mitoxantrone (FM). After R/high-dose cytosine-arabinoside and mitoxantrone (HAM) or R/carmustine/etoposide/cytarabine/melphalan (BEAM), the level of t(14;18)-positive cells dropped below the detection limit in 80% of patients.

CONCLUSIONS

LightCycler qPCR is a reliable method for quantitative molecular monitoring of t(14;18)-positive cells in BM and PB of patients with follicular lymphoma. It reflects the clinical characteristics of patients and allows assessment of response to different treatment regimens on a molecular level.

B-cell purging in autologous stem-cell transplantation for non-Hodgkin lymphoma

Autologous stem-cell transplantation is a common therapy for B-cell non-Hodgkin lymphoma. However, a concern with the procedure is the potential of malignant cells to reinfuse with the stem-cell graft. Thus attempts have been made to purge, or eliminate, malignant cells from the graft. The oldest, and most well studied, method for prevention of reinfusion is in vitro use of antibodies against B cells that bind or lyse malignant B cells and healthy cells, while leaving T cells and stem cells to be reinfused. In the past 5 years, investigators have used rituximab, an antibody against CD20, to purge malignant cells in vivo without any manipulation in vitro. Both conventional and new techniques have shown promise, but their exact role remains to be defined. We analysed data on the purging of B cells by use of antibodies in the setting of autologous transplantation, with emphasis on the emerging technique of in vivo purging.

Long-term follow-up of indolent lymphoma patients treated with high-dose sequential chemotherapy and autografting: evidence that durable molecular and clinical remission frequently can be attained only in follicular subtypes

PURPOSE

To evaluate the prognostic relevance of molecular monitoring of minimal residual disease in indolent lymphomas receiving high-dose sequential chemotherapy and autografting.

PATIENTS, MATERIALS, AND METHODS

A polymerase chain reaction- (PCR-)based strategy was used to evaluate the presence of residual tumor cells in a panel of 70 indolent lymphoma patients: 40 with follicular (FCL), 14 with small lymphocytic (SLL), and 16 with mantle-cell (MCL) lymphomas. They were treated either with first-line (n = 61) or second-line (n = 9) therapy with an intensified high-dose chemotherapy program followed by peripheral-blood progenitor cells autografting. The Bcl-1, Bcl-2, and immunoglobulin gene rearrangements were used as lymphoma-specific markers. Overall, a molecular marker was obtained from the diagnostic tissue in 60 of 70 patients (86%). Results The collection of PCR-negative cells and the achievement of posttransplantation molecular remission (MR) were common in patients with FCL subtype (54% and 70%, respectively), whereas they were not frequent among SLL and MCL (25% and 12.5%, respectively) patients. With a median molecular follow-up of 75 months, an 88% incidence of relapse was observed among patients never attaining MR. In contrast, relapse incidence was only 8% among patients attaining a durable MR (P <.005). At present, 26 patients (20 with FCL and six with non-FCL) are long-term survivors in absence of clinical and molecular disease.

CONCLUSION

Our results indicate that among indolent lymphomas, FCL and non-FCL subtypes show a significantly different behavior in terms of MR achievement, and MR after intensive chemotherapy and autografting is predictive for a prolonged disease-free survival, whereas persistent PCR positivity is associated with a high risk of relapse.

Infused CD34+ cell dose, but not tumour cell content of peripheral blood progenitor cell grafts, predicts clinical outcome in patients with diffuse large B-cell lymphoma and follicular lymphoma grade 3 treated with high-dose therapy

Previously, we have shown that patients with diffuse large B-cell lymphoma (DLBCL) transplanted with contaminated bone marrow (BM) generally have a poor outcome. Whether this is also the case when peripheral blood progenitor cell (PBPC) grafts are used is not known. Forty-three patients with chemosensitive DLBCL or follicular lymphoma grade 3 (FLgr3) were treated with high-dose therapy (HDT) and autologous stem cell support. Nine patients received purged grafts. Quantitative real-time polymerase chain reaction (QRT-PCR) for either the BCL2/IgH translocation or allele specific oligonucleotide (ASO) QRT-PCR for the immunoglobulin heavy chain (IgH) complementarity-determining region 3 were used. Nine of 25 (36%) PBPC grafts contained tumour cells as tested by QRT-PCR, including two grafts purged by CD34(+) cell enrichment combined with B-cell depletion. The level of contamination of the PBPC/CD34(+) cells ranged from 0 to 8.28%. No relationship could be shown between the total number of tumour cells infused and relapse. Patients receiving PCR-positive or PCR-negative PBPC grafts had similar progression-free survival (PFS) (P = 0.49). However, a significant difference was seen in PFS and overall survival (OS) for the patients given >/=6.1 x 10(6) CD34(+) cells/kg compared with those given <6.1 x 10(6) CD34(+) cells/kg (P = 0.01 and P < 0.05 respectively).

Efficiency of in vivo purging with rituximab prior to autologous peripheral blood progenitor cell transplantation in B-cellnon-Hodgkin’s lymphoma: a single institution study

BACKGROUND

Rituximab induces clinical response in advanced B-cell lymphoma and is efficient in removing circulating B-cell from peripheral blood. We therefore postulated that rituximab might be a useful in vivo purging agent before high-dose therapy in this setting.

PATIENTS AND METHODS

Fourteen patients with relapsed follicular, marginal zone and mantle cell lymphomas (11, two and one cases, respectively) and a PCR-detectable molecular marker were treated first with rituximab, then a mobilization chemotherapeutic regimen, followed by high-dose therapy with peripheral blood stem cell transplantation. PCR analyses were performed in peripheral blood before rituximab and during follow-up, and in harvest.

RESULTS

Harvests were free of PCR-detectable molecular marker in nine of the 11 studied cases (82%). After high-dose therapy, clinical complete remission was obtained in 13 (93%) patients and molecular remission in 11 (79%). With a median follow-up of 3 years, the 14 transplanted patients were alive, 11 of them remaining in clinical complete remission and eight in molecular remission at last follow-up.

CONCLUSION

Rituximab treatment followed by high dose therapy appears to be effective in achieving complete clinical and molecular response. In vivo harvest purging is predictive of prolonged clinical and molecular remission.

Evaluation of multiple recurrence events in superficial bladder cancer patients treated with intravesical bacillus Calmette-Guérin therapy using the Andersen-Gill's model

To evaluate factors affecting recurrence after intravesical bacillus Calmette-Guérin (BCG) therapy (Tokyo 172 strain), we reviewed data for 101 patients with superficial bladder cancer (pTa [n = 80] and pT1 [n = 21]) treated between 1985 and 1999. The median follow-up period was 58.9 months. Factors affecting the first tumour recurrence were evaluated using Cox's proportional hazards model and those affecting multiple recurrence with Andersen-Gill's model. The 5-year recurrence-free rate was 63% for all 101 patients. The recurrence frequency, defined as times per 100 patient-months of follow-up, greatly decreased from 7.3 +/- 9.6 (SD) before the instillation to 2.6 +/- 5.6 after the therapy (p < 0.0001). Patients with pT1 tumours tended to have earlier recurrence than those with pTa tumours (p = 0.06). Multivariate analysis using Cox's proportional hazards model revealed that a history of bladder cancer and pathological stage were independent factors affecting the first tumour recurrence after the BCG therapy. When multiple endpoints of recurrence were evaluated using the Andersen-Gill's model, number of tumours as well as a history of bladder cancer and pathological stage demonstrated significant links to tumour recurrence after the BCG therapy. The 5-year progression-free and 5-year survival rates were 89.3% and 85.3% for all the 101 patients, respectively. Because intravesical recurrence may involve multiple events during the clinical course of patients with bladder cancer, the Andersen-Gill's model appears useful for evaluation of risk factors.

Quantitative assessment of contaminating tumor cells in autologous peripheral blood stem cells of B-cell non-Hodgkin lymphomas using immunoglobulin heavy chain gene allele-specific oligonucleotide real-time quantitative-polymerase chain reaction

A real-time quantitative-polymerase chain reaction (RQ-PCR) targeting the immunoglobulin heavy chain (IgH) gene has been used for the quantification of minimal residual disease (MRD) in B-cell hematological malignancies. In non-Hodgkin lymphoma (NHL), experimental costs are increased, as a large number of primer-probe sets are required because of diversity, due to somatic and ongoing mutations of the IgH gene. We developed an allele-specific oligonucleotide (ASO) combined with a germline consensus probe-based RQ-PCR assay and examined MRD in peripheral blood stem cells (PBSC). The IgH consensus probes were adapted in seven (50%) of 14 amplifiable cases. Patients with heavily contaminating tumor cells in PBSC relapsed after PBSC transplantation. Our strategy will contribute to the development of a cost-efficient, precisely quantitative and systemic detection assay for MRD in NHL.

Clinical applications of CD34+ cell-selected peripheral blood stem cells

Peripheral blood stem cells (PBSC) are increasingly used for stem cell transplantation after high dose chemotherapy. CD34+ cell selection has also been done for use in autologous transplantation studies Bone marrow (BM) may contain tumor cells at the time of harvesting, and on re-infusion, these cells could contribute to a subsequent relapse. Similarly, tumor cell contamination of PBSC collections has been found in a number of studies. Therefore, purging contaminating tumor cells may prevent cases of relapse. As most tumor cell types do not express CD34 antigen, one of the most widespread applications of CD34+ cell selection is likely to be in tumor cell purging. Similarly, CD34+ cell selection has aided allogeneic transplantation studies. Acute graft-versus-host disease (aGVHD) is a major cause of morbidity and mortality in cases of allogeneic transplantation. As aGVHD is mediated by donor T cells, removal of T cells from the graft by CD34+ cell selection may ensure prophylaxis against aGVHD. Further, high-dose immunosuppression followed by CD34+ cell-selected stem cell rescue is theoretically reasonable as a therapeutic tool for patients with autoimmune disease resistant to conventional therapy. However, patients given T cell-depleted transplantation have an increased risk of opportunistic infection as well as malignancies related to immunosuppression; therefore, close monitoring is warranted. We describe here clinical applications of CD34+ cell-selected PBSC for a variety of diseases, with special emphasis on the efficacy as well as drawbacks of this novel technique.

PCR-detectable nonneoplastic Bcl-2/IgH rearrangements are common in normal subjects and cancer patients at diagnosis but rare in subjects treated with chemotherapy

PURPOSE

To assess whether nonneoplastic Bcl-2/IgH rearrangements act as a confounding factor in the setting of minimal residual disease analysis by evaluating their incidence in a panel of lymphoma-free subjects, including cancer-free donors and chemotherapy-naive and chemotherapy-treated cancer patients.

PATIENTS AND METHODS

A total of 501 nonlymphoma subjects have been assessed: 258 cancer-free patients and 243 patients with malignancies other than lymphoma, 112 of whom were chemotherapy-naive. Patients were primarily assessed by nested polymerase chain reaction (PCR), followed by real-time quantitative PCR if they scored positive. In addition, six initially PCR-positive cancer-free donors were prospectively reassessed by qualitative and quantitative PCR after 30 and 60 days.

RESULTS

The overall incidence of Bcl-2/IgH positivity was 9.6%, with a median number of 11 rearrangements per 1,000,000 diploid genomes (range, 0 to 2,845 rearrangements), as assessed by real-time PCR. The incidence was similar in healthy subjects and cancer patients at diagnosis (12% and 12.5%; P = not significant). In contrast, the incidence of this translocation was only 2.3% in chemotherapy-treated patients (P <.001). In addition, three initially PCR-positive cancer-free donors showed persistence of their rearrangements when assessed after 30 and 60 days.

CONCLUSION

The low incidence of nonneoplastic Bcl-2/IgH rearrangements following chemotherapy provides further evidence of the prognostic role of persistent PCR-positivity in the posttreatment molecular follow-up of follicular lymphoma patients.

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.

PCR detection of residual Bcl-2/IgH-positive cells after high-dose therapy with autologous stem cell transplantation is a prognostic factor for event-free survival in patients with low-grade follicular non-Hodgkin's lymphoma

This study was designed to evaluate the results of high-dose therapy followed by purged autologous stem cell transplantation (ASCT) for patients with low-grade follicular non Hodgkin's lymphoma (LGFL), and the prognostic significance of PCR detection of residual Bcl-2/IgH-positive cells after ASCT. Between 1992 and 1998, 49 patients with LGFL received total body irradiation and high-dose cyclophosphamide followed by purged ASCT. PCR amplification of the Bcl-2/IgH rearrangement was performed at diagnosis, on stem cell collections before and after purging and on bone marrow and blood samples after ASCT. With a median follow-up of 76 months (37-103) 34 patients remain alive and event-free. A total of 20 patients had disease recurrence, three patients developed secondary myelodysplastic syndrome (MDS). In all, 11 patients died; 10 deaths were because of recurrent disease, one because of MDS. Kaplan-Meier estimates of event-free survival (EFS) and overall survival (OS) at 5 years were 65% (+/-7%) and 77% (+/-6%), respectively. Patients who achieved a sustained molecular complete response (CR) had a lower risk of disease recurrence and experienced significantly longer EFS (93% (+/-6%) vs 11% (+/-7%) P=0.0008) and OS (100 vs 55% (+/-12%) P=0.0057). In conclusion, myeloablative therapy followed by purged ASCT may induce long EFS in patients with LGFL. The achievement of sustained molecular CR after ASCT improves EFS and OS.

Molecular Diagnostics

It is increasingly evident that molecular diagnostics, that is, the use of diagnostic testing to understand the molecular mechanisms of an individual patient’s disease, will be pivotal in the delivery of safe and effective therapy for many diseases in the future. A huge body of new information on the genetic, genomic and proteomic profiles of different hematopoietic diseases is accumulating. This chapter focuses on new technologies and advancements in understanding the molecular basis of hematologic disorders, providing an overview of new information and its significance to patient care.

In Section I, Dr. Braziel discusses the impact of new genetic information and research technologies on the actual practice of diagnostic molecular hematopathology. Recent and projected changes in methodologies and analytical strategies used by clinical molecular diagnostics laboratories for the evaluation of hematologic disorders will be discussed, and some of the challenges to clinical implementation of new molecular information and techniques will be highlighted.

In Section II, Dr. Shipp provides an update on current scientific knowledge in the genomic profiling of malignant lymphomas, and describes some of the technical aspects of gene expression profiling. Analysis methods and the actual and potential clinical and therapeutic applications of information obtained from genomic profiling of malignant lymphomas are discussed.

In Section III, Dr. Liotta presents an update on proteomic analysis, a new and very active area of research in hematopoietic malignancies. He describes new technologies for rapid identification of different important proteins and protein networks, and the potential therapeutic and prognostic value of the elucidation of these proteins and protein pathways in the clinical care of patients with malignant lymphomas.

Molecular remission and non-Hodgkin's lymphoma

Non-Hodgkin's lymphomas are highly sensitive to treatment and complete clinical responses are often achieved. However, disease recurrence is common and is caused by the persistence of malignant lymphoma cells at a level below the limits of detection by conventional assessment such as clinical examination, bone marrow morphology and CT scans. This minimal residual disease can be detected using molecular techniques such as the polymerase chain reaction (PCR), and treatments capable of eliminating minimal residual disease are described as producing molecular remission. Molecular assessment is now commonly used as a measure of outcome in clinical trials of novel therapies for the treatment of lymphoma. The evidence for using molecular remission as a surrogate marker of clinical response in this setting is reviewed and the significance of minimal residual disease in determining prognosis and planning treatment strategies is addressed.

Insights into the molecular pathogenesis of follicular lymphoma arising from analysis of geographic variation

Incidence rates of follicular lymphoma (FL) inexplicably vary markedly between Western and Asian countries. A hallmark of FL is the bcl-2 translocation, characterized by 1 of 2 common breakpoints known as major breakpoint region (MBR) and minor cluster region (mcr). We analyzed previously published data to compare rates of bcl-2 translocation in FL across geographic regions. Available data from the literature suggest that the incidence of bcl-2 in healthy persons in the absence of FL may be as high as 50% in Western and Asian populations. However, in FL our results show that the frequency of bcl-2 positivity was significantly higher for US than for Asian populations (P <.0001). This pattern persisted for MBR and mcr subgroups. We conclude that a significant gradient exists in the bcl-2 frequency between these FL populations. We therefore suggest that the relatively low incidence of FL in Asian populations is caused not by a lower frequency of bcl-2 rearrangements in healthy populations but by distinct molecular pathways developing in different geographic regions that nonetheless culminate in FL, which is morphologically similar but molecularly distinct. Studies demonstrating differences in clinical characteristics according to the presence or absence of bcl-2 rearrangements support this concept. Thus we hypothesize that FL may in fact be a heterogeneous malignancy encompassing entities with distinct molecular pathogenesis and potentially distinct clinical manifestations. If these findings were confirmed in prospective studies, it would imply that different etiologic or genetic factors might influence the development of FL across separate regions.

Monitoring disease in lymphoma and CLL patients using molecular techniques

Over the past decade considerable advances have been made in the sensitivity of detection of residual lymphoma and leukaemia cells. Assays based on the polymerase chain reaction (PCR) can detect one tumour cell in up to 10(5) to 10(6) normal cells. The identification and cloning of breakpoints associated with specific chromosomal translocations has made possible the application of these techniques to a variety of lymphoid malignancies. In parallel, B cell malignancies exhibit rearrangements of their immunoglobulin genes that are also suitable targets for PCR amplification to identify residual cells. Although these techniques provide a useful adjunct to standard methods of detection and diagnosis, their role in determining disease outcome remains investigational. There is confusion as to whether it is necessary to eradicate PCR-detectable lymphoma cells for cure, so it is not yet possible to determine whether the detection of residual lymphoma cells by PCR is an indication to continue therapy.

Positron emission tomography with [18F]2-fluoro-D-2-deoxyglucose (FDG-PET) predicts relapse of malignant lymphoma after high-dose therapy with stem cell transplantation

We have determined the predictive value of [18F]2-fluoro-2-deoxy-glucose (FDG-PET) in patients with Hodgkin's disease (HD) and aggressive non-Hodgkin's lymphoma (NHL) scheduled for high-dose therapy with stem cell transplantation (HDT/SCT). Inclusion criteria were the presence of an FDG-PET scan after chemotherapy (ChT) within 8 weeks prior to HDT/SCT and available follow-up data. Sixteen patients (10 NHL and six HD) were observed during a follow-up period of 4 to 28 months (median 13 months). Before SCT, five patients had a negative PET, three were weakly positive, two moderately positive, and six strongly positive. None of the five patients with a negative PET before HDT/SCT relapsed and two of three patients with a weakly positive scan are still in remission after HDT/SCT. Of eight patients with a moderate or high positive PET before HDT/SCT, seven relapsed and one died of early HDT/SCT related complications (P< 0.01). Three of eight relapsing patients died of lymphoma 5 to 10 months after SCT and in one additional patient not responding to HDT/SCT, the main cause of death was chronic toxicity 4 months after transplantation. After 12 months, in PET-negative patients the overall and relapse-free survival was 100%, in PET-positive patients 55% and 18%, respectively. In NHL, two patients with negative PET, but with an age-adjusted international prognostic index (AaIPI) of 2 and one with AaIPI = 1 are still in remission. In the seven PET-positive subjects, one patient with AaIPI = 0, three with AaIPI = 1, and two with AaIPI = 2 relapsed. We conclude that FDG-PET is accurate in the prediction of relapse prior to HDT/SCT in patients with lymphoma. It provides additional information when compared with the AaIPI.

Association between high interleukin-6 levels and adverse outcome after autologous haemopoietic stem cell transplantation

We studied interleukin-6 (IL-6) levels on the day of transplantation in 31 patients undergoing autologous haemopoietic stem cell transplantation (SCT) (either peripheral blood stem cell transplantation (PBSCT) or bone marrow transplantation (BMT)) for neoplastic diseases to determine if there was a relationship between IL-6 level and rate of haemopoietic recovery, length of stay in hospital, and survival. There was no apparent delay in post-transplant recovery associated with elevated IL-6 levels. However, increased values of IL-6 tended to be associated with an increased length of stay in hospital (P = 0.083). There was a highly significant adverse association between higher IL-6 levels and survival following transplantation (P = 0.0001). This association remained significant (P = 0.013) in the uniform subgroup of patients with malignant lymphoma with chemosensitive disease who had undergone BMT (that is, excluding patients who had undergone PBSCT) (n = 13). Knowledge of IL-6 levels on the day of transplant has the potential to provide valuable prognostic information in patients undergoing autologous haemopoietic SCT.

A validated real-time quantitative PCR approach shows a correlation between tumor burden and successful ex vivo purging in follicular lymphoma patients

OBJECTIVE

Purging procedures are increasingly used to provide stem cell collections devoid of contaminating tumor cells. In follicle center lymphoma (FCL), most approaches eradicate polymerase chain reaction (PCR);-detectable disease in only a fraction of harvests undergoing ex vivo manipulation. In this study we evaluated whether there is a relationship between tumor burden of stem cell harvests and successful clearance of PCR-detectable disease following ex vivo manipulation.

MATERIALS AND METHODS

To address this issue, we developed a real-time PCR approach for quantitative measurement of tumor contamination using the bcl-2 rearrangement. Real-time PCR was used to evaluate the relationship between tumor burden of stem-cell harvests and purging effectiveness in PCR(+) samples derived from 10 FCL patients. Ex vivo purging was performed using the MaxSep cell separator (Baxter Immunotherapy, Deerfield, IL, USA).

RESULTS

Our real-time PCR method proved effective, sensitive, accurate, and reproducible. Four collections were successfully cleared of minimal residual disease (MRD) whereas six remained PCR(+). Real-time PCR showed that the four collections successfully cleared of MRD had a prepurging tumor burden significantly lower than those remaining PCR(+) (p = 0.04).

CONCLUSION

This study provides the first evidence that evaluation of tumor burden in stem-cell harvests by real-time PCR can predict the effectiveness of therapeutic intervention in non-Hodgkin's lymphoma. Based on these findings, we foresee a more widespread use of this technique to evaluate the impact of different therapeutic approaches in FCL.

In vivo depletion of B cells using a combination of high-dose cytosine arabinoside/mitoxantrone and rituximab for autografting in patients with non-Hodgkin's lymphoma

We performed a pilot study including rituximab (Mabthera; IDEC-C2B8, Hoffmann-La Roche) with a sequential high-dose therapy protocol in 15 patients with follicular and three patients with mantle cell lymphoma and studied the potential of the chemoimmunotherapy to induce depletion of malignant B cells in vivo. Our treatment protocol included induction with three cycles of CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) chemotherapy, followed by peripheral blood stem cell (PBSC) mobilization using high-dose cytosine arabinoside (2 g/m2 every 12 h, days 1 and 2) and mitoxantrone (10 mg/m2, days 2 and 3) (HAM), preceeded by rituximab (375 mg/m2). The proportion of CD19+ B cells in blood and bone marrow decreased from 1.2 +/- 0.4% to 0.13 +/- 0. 1% (P = 0.01) and from 2.7 +/- 0.8% to 0.8 +/- 0.5% (P = 0.03) respectively. The number of t(14;18)-positive cells in blood and bone marrow progressively decreased with treatment, as assessed by the quantitative real-time PCR assay in four patients. Conversion to PCR-negativity was achieved in the peripheral blood (PB) of seven informative patients. Leucaphereses were performed during the granulocyte colony-stimulating factor (G-CSF)-supported leucocyte recovery phase. In 17 of 18 patients, a median of 15.1 x 106 CD34+ cells/kg body weight (BW) could be harvested by a single procedure for enrichment by an immunomagnetic method. Leucapheresis products contained 51.3 +/- 28.8 x 104 CD19+ B cells/kg BW (mean) and were t(14;18) PCR negative in all seven informative patients. These data compare favourably with results obtained in patients treated with the same regimen without rituximab. The high-dose therapy (n = 12 patients), including total body irradiation (14.4 Gy) and cyclophosphamide (200 mg/kg BW), was also preceeded by rituximab. Recovery of neutrophils to > 0.5 x 109/l and of platelets to > 20 x 109/l required a median of 13.5 and 11.5 d (range 11-24 and 9-24 d) respectively. In conclusion, the addition of the CD20 antibody to chemotherapy ensured tumour depletion in vivo and allowed the collection of PBSCs devoid of tumour cells and with conserved engraftment capability.

Prognostic factors for the clinical outcome of patients with follicular lymphoma following high-dose therapy and peripheral blood stem cell transplantation (PBSCT)

This is a report on 111 patients with advanced stage follicular lymphoma who where autografted using PBSC. Seventy patients were enrolled in first remission, whereas 41 were treated in second or higher remission. High-dose therapy consisted of total body irradiation plus cyclophosphamide in 103 patients, while eight patients received BEAM (carmustine, etoposide, cytosine-arabinoside, melphalan). Autografts contained 8.1 +/- 0.6 x 106 CD34+ cells/kg body weight. At a median follow-up of 44.2 months from PBSCT (range 4.9-77.4 months), 93 patients are alive, with a probability of overall and relapse-free survival (RFS) of 83% and 64%, respectively. A significantly higher probability of relapse was associated with male gender, involvement of more than eight lymph node areas, extra-nodal manifestations other than bone marrow and PBSCT performed in second or higher remission. In the latter group of patients, previous radiotherapy was associated with poor prognosis. The relevance of chemosensitivity as a prognostic factor was reflected by a better RFS in patients who had achieved complete remission at the time of PBSC mobilization. In a multivariate analysis, involvement of eight or more lymph nodes and high-dose therapy performed in second or higher remission were independent prognostic factors.

Stem cell transplantation for indolent lymphoma

Stem cell transplantation (SCT) has become the treatment of choice for patients with relapsed aggressive non-Hodgkin's lymphoma (NHL). The role of SCT in the management of patients with low-grade NHL remains more controversial, although increasing numbers of patients with advanced-stage follicular lymphoma, mantle cell lymphoma, and chronic lymphocytic leukemia are now undergoing SCT. To date, most patients with NHL have been treated with autologous SCT, currently using peripheral blood stem cells (PBSC) mobilized by chemotherapy and recombinant growth factors. There is increasing concern regarding toxicity of autologous SCT, especially the higher than expected long-term risk of development of myelodysplastic syndrome. This, among other factors, has led to renewed interest in the role of allogeneic SCT for patients with NHL. A major advantage of allogeneic SCT is the potential to exploit a graft-versus-lymphoma effect, and many studies are underway exploring the possibility of manipulating donor cells to maximize T cell responsiveness against lymphoma.