Targeted therapy of cancer stem cells: inhibition of mTOR in pre-clinical and clinical research

Cancer stem cells (CSCs) are a type of stem cell that possesses not only the intrinsic abilities of stem cells but also the properties of cancer cells. Therefore, CSCs are known to have self-renewal and outstanding proliferation capacity, along with the potential to differentiate into specific types of tumor cells. Cancers typically originate from CSCs, making them a significant target for tumor treatment. Among the related cascades of the CSCs, mammalian target of rapamycin (mTOR) pathway is regarded as one of the most important signaling pathways because of its association with significant upstream signaling: phosphatidylinositol 3‑kinase/protein kinase B (PI3K/AKT) pathway and mitogen‑activated protein kinase (MAPK) cascade, which influence various activities of stem cells, including CSCs. Recent studies have shown that the mTOR pathway not only affects generation of CSCs but also the maintenance of their pluripotency. Furthermore, the maintenance of pluripotency or differentiation into specific types of cancer cells depends on the regulation of the mTOR signal in CSCs. Consequently, the clinical potential and importance of mTOR in effective cancer therapy are increasing. In this review, we demonstrate the association between the mTOR pathway and cancer, including CSCs. Additionally, we discuss a new concept for anti-cancer drug development aimed at overcoming existing drawbacks, such as drug resistance, by targeting CSCs through mTOR inhibition.

Deregulated transcription factors in the emerging cancer hallmarks

Cancer progression is a multifaceted process that entails several stages and demands the persistent expression or activation of transcription factors (TFs) to facilitate growth and survival. TFs are a cluster of proteins with DNA-binding domains that attach to promoter or enhancer DNA strands to start the transcription of genes by collaborating with RNA polymerase and other supporting proteins. They are generally acknowledged as the major regulatory molecules that coordinate biological homeostasis and the appropriate functioning of cellular components, subsequently contributing to human physiology. TFs proteins are crucial for controlling transcription during the embryonic stage and development, and the stability of different cell types depends on how they function in different cell types. The development and progression of cancer cells and tumors might be triggered by any anomaly in transcription factor function. It has long been acknowledged that cancer development is accompanied by the dysregulated activity of TF alterations which might result in faulty gene expression. Recent studies have suggested that dysregulated transcription factors play a major role in developing various human malignancies by altering and rewiring metabolic processes, modifying the immune response, and triggering oncogenic signaling cascades. This review emphasizes the interplay between TFs involved in metabolic and epigenetic reprogramming, evading immune attacks, cellular senescence, and the maintenance of cancer stemness in cancerous cells. The insights presented herein will facilitate the development of innovative therapeutic modalities to tackle the dysregulated transcription factors underlying cancer.

Exploring the dynamic interplay between cancer stem cells and the tumor microenvironment: implications for novel therapeutic strategies

Cancer stem cells (CSCs) have emerged as key contributors to tumor initiation, growth, and metastasis. In addition, CSCs play a significant role in inducing immune evasion, thereby compromising the effectiveness of cancer treatments. The reciprocal communication between CSCs and the tumor microenvironment (TME) is observed, with the TME providing a supportive niche for CSC survival and self-renewal, while CSCs, in turn, influence the polarization and persistence of the TME, promoting an immunosuppressive state. Consequently, these interactions hinder the efficacy of current cancer therapies, necessitating the exploration of novel therapeutic approaches to modulate the TME and target CSCs. In this review, we highlight the intricate strategies employed by CSCs to evade immune surveillance and develop resistance to therapies. Furthermore, we examine the dynamic interplay between CSCs and the TME, shedding light on how this interaction impacts cancer progression. Moreover, we provide an overview of advanced therapeutic strategies that specifically target CSCs and the TME, which hold promise for future clinical and translational studies in cancer treatment.

CAR T-Cell therapy for the management of mantle cell lymphoma

Mantle cell lymphoma (MCL) is a subtype of Non-Hodgkin lymphoma (NHL) of mature B-cells characterized by translocation, which is typically due to excess expression of Cyclin D1. Although with the progress in our knowledge of the causes for MCL and available treatments for MCL, this cancer is still incurable. Age, male gender, rapid advancement, significant nodal involvement, elevated serum lactate dehydrogenase level, and prognostic indications including increased expression of Ki-67 and presence of TP53 mutation, are symbols of poor outcome. Advanced immunotherapy using chimeric antigen receptor (CAR)-T cells is advantageous for patients suffering from B-cell malignancies and MCL. Targeting B-cell antigens on the cell surface is a feasible approach in re-occurring (R/R) MCL because of significant responses obtained in other B-cell cancers. USFDA has approved brexucabtagene autoleucel (Tecartus, KTE-X19), a novel CAR T-cell therapy to be used in patients with MCL who have not responded to previous treatments or have relapsed. The FDA approved this new treatment depending on the outcomes of the ZUMA-2 clinical trial. Serious adverse reactions, moderate anti-tumor activity, allergen withdrawal, antigen escape, limited tumor infiltration, and trafficking are major barriers to successful CAR T-cell therapy. This review is a brief synopsis of the development of CAR T-cell therapy for MCL.

Cancer stem cells (CSCs): key player of radiotherapy resistance and its clinical significance

Cancer stem cells (CSCs) are self-renewing and slow-multiplying micro subpopulations in tumour microenvironments. CSCs contribute to cancer's resistance to radiation (including radiation) and other treatments. CSCs control the heterogeneity of the tumour. It alters the tumour's microenvironment cellular singling and promotes epithelial-to-mesenchymal transition (EMT). Current research decodes the role of extracellular vesicles (EVs) and CSCs interlink in radiation resistance. Exosome is a subpopulation of EVs and originated from plasma membrane. It is secreted by several active cells. It involed in cellular communication and messenger of healthly and multiple pathological complications. Exosomal biological active cargos (DNA, RNA, protein, lipid and glycan), are capable to transform recipient cells' nature. The molecular signatures of CSCs and CSC-derived exosomes are potential source of cancer theranostics development. This review discusse cancer stem cells, radiation-mediated CSCs development, EMT associated with CSCs, the role of exosomes in radioresistance development, the current state of radiation therapy and the use of CSCs and CSCs-derived exosomes biomolecules as a clinical screening biomarker for cancer. This review gives new researchers a reason to keep an eye on the next phase of scientific research into cancer theranostics that will help mankind.

Bendamustine in combination with ofatumumab as first line treatment for elderly patients with mantle cell lymphoma: a phase II risk-adapted design

This study evaluated ofatumumab (Ofa), an anti-CD20 monoclonal antibody, alone or with bendamustine (Benda), in transplant-ineligible patients with mantle cell lymphoma. Low-risk patients received Ofa monotherapy. Non-responders received subsequent treatment with Benda-Ofa. Six patients received Ofa monotherapy and 3 patients crossed over to Bend-Ofa. Twenty-four high-risk patients were initially treated with Benda-Ofa. The overall response rate for patients treated with Ofa monotherapy was 1/6 (17%) and 23/25 (92%) for patients treated with Benda-Ofa. With a median follow-up of 8.6 years, all Ofa patients progressed with a median progression-free survival (PFS) of 0.6 years (95% CI 0.31-NR) and remain alive. With a median follow-up of 6.3 years, Bend-Ofa treated patients had median PFS 2.5 years (95% CI 1.8-NR) and a median overall survival of 7.4 years (95% CI 5.8-NR). Benda-Ofa had a favorable adverse event profile and efficacy similar, but not clearly superior, to those reported for Benda-Rituximab.

Cancer stem cell plasticity and its implications in the development of new clinical approaches for oral squamous cell carcinoma

Oral squamous cell carcinoma (SCC) represents a major worldwide disease burden, with high rates of recurrence and metastatic spread following existing treatment methods. Populations of treatment resistant cancer stem cells (CSCs) are well characterised in oral SCC. These populations of CSCs engage the cellular programme known as epithelial mesenchymal transition (EMT) to enhance metastatic spread and therapeutic resistance. EMT is characterised by specific morphological changes and the expression of certain cell surface markers that represent a transition from an epithelial phenotype to a mesenchymal phenotype. This process is regulated by several cellular pathways that interact both horizontally and hierarchically. The cellular changes in EMT occur along a spectrum, with sub-populations of cells displaying both epithelial and mesenchymal features. The unique features of these CSCs in terms of their EMT state, cell surface markers and metabolism may offer new druggable targets. In addition, these features could be used to identify more aggressive disease states and the opportunity to personalise therapy depending on the presence of certain CSC sub-populations.

Tumour Microenvironment Stress Promotes the Development of Drug Resistance

Multi-drug resistance (MDR) is a leading cause of cancer-related death, and it continues to be a major barrier to cancer treatment. The tumour microenvironment (TME) has proven to play an essential role in not only cancer progression and metastasis, but also the development of resistance to chemotherapy. Despite the significant advances in the efficacy of anti-cancer therapies, the development of drug resistance remains a major impediment to therapeutic success. This review highlights the interplay between various factors within the TME that collectively initiate or propagate MDR. The key TME-mediated mechanisms of MDR regulation that will be discussed herein include (1) altered metabolic processing and the reactive oxygen species (ROS)-hypoxia inducible factor (HIF) axis; (2) changes in stromal cells; (3) increased cancer cell survival via autophagy and failure of apoptosis; (4) altered drug delivery, uptake, or efflux and (5) the induction of a cancer stem cell (CSC) phenotype. The review also discusses thought-provoking ideas that may assist in overcoming the TME-induced MDR. We conclude that stressors from the TME and exposure to chemotherapeutic agents are strongly linked to the development of MDR in cancer cells. Therefore, there remains a vast area for potential research to further elicit the interplay between factors existing both within and outside the TME. Elucidating the mechanisms within this network is essential for developing new therapeutic strategies that are less prone to failure due to the development of resistance in cancer cells.

Direct targeting of cancer cells with antibodies: What can we learn from the successes and failure of unconjugated antibodies for lymphoid neoplasias?

Following approval in 1997 of the anti-CD20 antibody rituximab for the treatment of B-NHL and CLL, many other unconjugated IgG1 MAbs have been tested in pre-clinical and clinical trials for the treatment of lymphoid neoplasms. Relatively few have been approved however and these are directed against a limited number of target antigens (CD20, CD52, CCR4, CD38, CD319). We review here the known biological properties of these antibodies and discuss which factors may have led to their success or may, on the contrary, limit their clinical application. Common factors of the approved MAbs are that the target antigen is expressed at relatively high levels on the neoplastic targets and their mechanism of action is mostly immune-mediated. Indeed most of these MAbs induce ADCC and phagocytosis by macrophages, and many also activate complement, leading to target cell lysis. In contrast direct cell death induction is not a common feature but may enhance efficacy in some cases. Interestingly, a key factor for the success of several MAbs appears to be their capacity to skew immunity towards an anti-tumour mode, by inhibiting/depleting suppressor cells and/or activating immune cells within the microenvironment, independently of FcγRs. We also expose here some of the strategies employed by industry to expand the clinical use of these molecules beyond their original indication. Interestingly, due to the central role of lymphocytes in the control of the immune response, several of the antibodies are now successfully used to treat many different autoimmune diseases and have also been formally approved for some of these new indications. There is little doubt that this trend will continue and that the precise mechanisms of therapeutic MAbs will be further dissected and better understood in the context of both tumour immunology and autoimmunity.

Mantle Cell Lymphoma: Contemporary Diagnostic and Treatment Perspectives in the Age of Personalized Medicine

Mantle cell lymphoma is a clinically heterogeneous disease occurring within a heterogeneous patient population, highlighting a need for personalized therapy to ensure optimal outcomes. It is therefore critical to understand the benefits and risks associated with both intensive and deintensified approaches. In the following review we provide a therapeutic roadmap to strategically guide treatment for newly diagnosed and relapsed/refractory patients highlighting pivotal and recently published results involving known and novel therapies.

Reversal of cardiomyopathy with tocilizumab in a case of HIV-negative Castleman's disease

The association between Castleman's disease (CD) and cardiomyopathy has been rarely reported and the optimal therapeutic approach remains unknown. We report a previously healthy 20-year-old African American female who presented with fever, dyspnea, anasarca, and generalized lymphadenopathy. Diagnostic workup, including an axillary lymph node biopsy, revealed that she had human immunodeficiency virus-negative and human herpes virus-8-negative multicentric CD. She had a non-anaphylactoid infusion reaction during her fourth rituximab infusion. A few weeks later, she developed new-onset severe cardiomyopathy requiring inotropic therapy, warranting consideration for left ventricular assist device. Several clinical clues indicated her new-onset heart failure was a manifestation of her CD. Interestingly, a trial of tocilizumab (an anti-interleukin-6 receptor monoclonal antibody) resulted in complete resolution of her cardiomyopathy and other manifestations of CD. Tocilizumab received orphan drug approval for the treatment of CD in Japan, but is not yet approved for this indication in the United States. Clinicians should be aware of its potential clinical utility in CD.

Clinical review: Serious adverse events associated with the use of rituximab - a critical care perspective

The advent of biologic agents has provided a more specific and targeted approach to the treatment of various hematological malignancies and other autoimmune disorders. Such biologic agents have been relatively well tolerated with fewer adverse events reported as compared with many other chemotherapeutic agents. Rituximab is a monoclonal antibody to the B-cell marker CD20 and is a common biologic agent widely used for the treatment of B-cell lymphoma, lymphoproliferative disorders, and inflammatory conditions that are refractory to conventional treatment, including rheumatoid arthritis and some vasculitides. However, through randomized controlled trials and post-marketing surveillance, an increasing number of serious adverse events are being associated with the use of rituximab, often leading to or complicating an intensive care unit admission. The purpose of this review is to focus on the severe complications that are associated with the use of rituximab and that require critical care. Management and prevention strategies for the most common complications along with some examples of its uses within the critical care setting are also discussed.

Immunochemotherapy and autologous stem-cell transplantation for untreated patients with mantle-cell lymphoma: CALGB 59909

PURPOSE Mantle-cell lymphoma (MCL) is an aggressive B-cell non-Hodgkin's lymphoma with a poor prognosis. We explored the feasibility, safety, and effectiveness of an aggressive immunochemotherapy treatment program that included autologous stem-cell transplantation (ASCT) for patients up to age 69 years with newly diagnosed MCL. PATIENTS AND METHODS The primary end point was 2-year progression-free survival (PFS). A successful trial would yield a 2-year PFS of at least 50% and an event rate (early progression plus nonrelapse mortality) less than 20% at day +100 following ASCT. Seventy-eight patients were treated with two or three cycles of rituximab combined with methotrexate and augmented CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone). This treatment was followed by intensification with high doses of cytarabine and etoposide combined with rituximab and filgrastim to mobilize autologous peripheral-blood stem cells. Patients then received high doses of carmustine, etoposide, and cyclophosphamide followed by ASCT and two doses of rituximab. Results There were two nonrelapse mortalities, neither during ASCT. With a median follow-up of 4.7 years, the 2-year PFS was 76% (95% CI, 64% to 85%), and the 5-year PFS was 56% (95% CI, 43% to 68%). The 5-year overall survival was 64% (95% CI, 50% to 75%). The event rate by day +100 of ASCT was 5.1%. CONCLUSION The Cancer and Leukemia Group B 59909 regimen is feasible, safe, and effective in patients with newly diagnosed MCL. The incorporation of rituximab with aggressive chemotherapy and ASCT may be responsible for the encouraging outcomes demonstrated in this study, which produced results comparable to similar treatment regimens.

Expanding therapeutic options in mantle cell lymphoma

Mantle cell lymphoma (MCL) still carries a poor prognosis. Chemoimmunotherapy (combination with rituximab) is the routine first-line therapy, although data strongly suggest a benefit from intensification through high-dose therapy with stem cell transplantation consolidation or dose-intense chemotherapy with HyperCVAD (fractionated cyclophosphamide/vincristine/doxorubicin/dexamethasone)/rituximab. Unfortunately, most patients still experience relapse, and a multitude of novel agents are currently being tested in this setting, including proteasome inhibitors with bortezomib (the first of its class and first Food and Drug Administration-approved drug in MCL), mammalian target of rapamycin inhibitors, Bcl-2 inhibitors, and antiangiogenesis agents, among others. Because of the relative rarity of the disease-MCL represents 6% of non-Hodgkin lymphoma-an obvious effort is needed to enroll patients on clinical trials. Not surprisingly, as in other non-Hodgkin lymphomas, MCL appears more and more as a heterogeneous disease, which might impact future clinical trial design through pharmacogenomics and hopefully help us develop smaller "molecular" relevant trials.

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.

New Directions in the Treatment of Mantle Cell Lymphoma: An Overview

Mantle cell lymphoma (MCL) is one of the most challenging lymphomas to treat. In the first-line setting, high-dose therapy (HDT) and autologous stem cell transplantation or hyperCVAD/rituximab suggest benefit, especially in patients aged < 60 years. Nucleoside analogue-based regimens represent an alternate option in patients ineligible for HDT. Fludarabine in combination with cyclophosphamide or mitoxantrone has shown activity, and the results were superior with the addition of rituximab. Other cytotoxic agents, such as cladribine, clofarabine, or bendamustin, showed promising activity as well. A variety of new monoclonal antibody (MoAb) agents, such as humanized anti-CD20, alemtuzumab, anti-HLA-DR, anti-CD22 (as an immunotoxin carrier), anti-CD40, as well as MoAb-targeting TRAIL-R1 and TRAIL-R2 are being tested. Radioimmunotherapy with Yttrium 90-ibritumomab tiuxetan and Iodine 131 tositumomab have been tested alone or in combination with chemotherapy, including as part of HDT and autologous stem cell transplantation, in which they showed the best results. New vaccine modalities are exploring the use of tumor cell-based vaccines or of agents that block or activate costimulatory pathways/molecules, such as CTLA-4-Ig. Allogenic transplantation represents a potential curative option for MCL, especially nonmyeloablative transplantation, more feasible in that population. A plethora of novel biologic agents have surfaced, such as bortezomib, temsirolimus, thalidomide, lenalidomide, MoAb anti-vascular endothelial growth factor or vascular endothelial growth factor-Trap, and flavopiridol. Other targets include gene transcription through histone regulation; nuclear factor-ķB pathway; protein kinase C inhibitors; small-molecules targeting apoptosis, such as antisense Bcl-2, pan-Bcl-2 family member inhibitors; MoAb agonists of cell death receptors; caspases regulators (inhibitors of apoptosis proteins, survivin); and MDM2 antagonist regulators of p53. A molecular approach to define biomarkers might help identify subgroups of patients and help develop rational therapies.

Single agent rituximab in patients with follicular or mantle cell lymphoma: clinical and biological factors that are predictive of response and event-free survival as well as the effect of rituximab on the immune system: a study of the Swiss Group for Clinical Cancer Research (SAKK)

BACKGROUND

Predictive factors of rituximab efficacy and its effect on the immune system are still not defined.

PATIENTS AND METHODS

Three hundred and six patients with follicular or mantle cell lymphoma received four weekly doses of rituximab (induction) and no further treatment (arm A) or four more doses at 2-month intervals (arm B).

RESULTS

Response rate to induction was 44%. Independent predictive factors for response were disease bulk <5 cm, follicular histology, normal hemoglobin and low lymphocyte count. Factors associated with event-free survival (EFS) were having responded to induction, having received not more than one line of therapy, Ann Arbor stage I-III, high lymphocyte count, disease bulk <5 cm, Fc-gamma receptor genotype VV and receiving prolonged treatment. B cells were suppressed by treatment but recovered after a median of 12 months in arm A and 18 months in arm B. The median IgM level after 1 year was normal in arm A but was decreased to 73% of baseline in arm B. We observed 24 serious adverse events, equally distributed between arms. Ten patients receiving induction only and six patients receiving prolonged treatment developed a second tumor.

CONCLUSIONS

We defined the characteristics predicting response and EFS to rituximab. Prolonged treatment results in longer EFS at the cost of a longer reduction in B cell and IgM levels, but without additional clinical toxicity.

Phase II trial of single-agent temsirolimus (CCI-779) for relapsed mantle cell lymphoma

PURPOSE

Mantle cell lymphoma (MCL) is characterized by a t(11;14) resulting in overexpression of cyclin D1 messenger RNA. This study tested whether temsirolimus (previously known as CCI-779), an inhibitor of the mammalian target of rapamycin kinase that regulates cyclin D1 translation, could produce tumor responses in patients with MCL.

PATIENTS AND METHODS

Patients with relapsed or refractory MCL were eligible to receive temsirolimus 250 mg intravenously every week as a single agent. Patients with a tumor response after six cycles were eligible to continue drug for a total of 12 cycles or two cycles after complete remission, and were then observed without maintenance.

RESULTS

Thirty-five patients were enrolled and were assessable for toxicity; one patient had MCL by histology but was cyclin D1 negative and was ineligible for efficacy. The median age was 70 years (range, 38 to 89 years), 91% were stage 4, and 69% had two or more extranodal sites. Patients had received a median of three prior therapies (range, one to 11), and 54% were refractory to the last treatment. The overall response rate was 38% (13 of 34 patients; 90% CI, 24% to 54%) with one complete response (3%) and 12 partial responses (35%). The median time-to-progression in all patients was 6.5 months (95% CI, 2.9 to 8.3 months), and the duration of response for the 13 responders was 6.9 months (95% CI, 5.2 to 12.4 months). Hematologic toxicities were the most common, with 71% (25 of 35 patients) having grade 3 and 11% (four of 35 patients) having grade 4 toxicities observed. Thrombocytopenia was the most frequent cause of dose reductions but was of short duration, typically resolving within 1 week.

CONCLUSIONS

Single-agent temsirolimus has substantial antitumor activity in relapsed MCL. This study demonstrates that agents that selectively target cellular pathways dysregulated in MCL cells can produce therapeutic benefit. Further studies of this agent in MCL and other lymphoid malignancies are warranted.

Rituximab therapy for patients with newly diagnosed, advanced-stage, follicular grade I non-Hodgkin's lymphoma: a phase II trial in the North Central Cancer Treatment Group

PURPOSE

Patients with newly diagnosed, advanced-stage, follicular grade 1 non-Hodgkin's lymphoma (NHL) are often asymptomatic and can be observed without immediate chemotherapy. The goals of this study were to assess the overall response rate (ORR) to rituximab in this patient population and to determine the time-to-progression (TTP) and time-to-subsequent-chemotherapy (TTSC).

PATIENTS AND METHODS

Eligible patients had untreated follicular grade 1 NHL, and measurable stage III/IV disease. Patients received rituximab 375 mg/m(2) intravenous weekly x 4 doses and were then followed for response and progression; no maintenance therapy was provided.

RESULTS

Thirty-seven patients were accrued; one patient was ineligible. The median age was 59 years (range, 29 to 83 years). Six patients (18%) had elevated lactate dehydrogenase levels. The ORR was 72%, with 36% complete remissions. Fourteen (39%) of 36 patients remain in unmaintained remission, two died without disease progression, and three died with disease progression. Twenty (56%) of 36 patients have disease progression. The median TTP was 2.2 years (95% CI, 1.3 to not yet reached). Eighteen patients have subsequently been treated with chemotherapy, with a median TTSC of 2.3 years (95% CI, 1.6 to not yet reached). Patients with a high lactate dehydrogenase level had a lower ORR of 33% and a short TTP of only 6 months.

CONCLUSION

Rituximab can be safely administered to patients with advanced-stage follicular grade 1 NHL with efficacy and minimal toxicity. This therapy is highly active and offers an acceptable alternative to observation in this patient population. Patients with high LDH should not be considered for rituximab monotherapy.

Effect of single-agent rituximab given at the standard schedule or as prolonged treatment in patients with mantle cell lymphoma: a study of the Swiss Group for Clinical Cancer Research (SAKK)

PURPOSE

To evaluate the effect of single-agent rituximab given at the standard or a prolonged schedule in patients with newly diagnosed, or refractory or relapsed mantle cell lymphoma (MCL).

PATIENTS AND METHODS

After induction treatment with the standard schedule (375 mg/m2 weekly x 4), patients who were responding or who had stable disease at week 12 from the start of treatment were randomly assigned to no further treatment (arm A) or prolonged rituximab administration (375 mg/m2) every 8 weeks for four times (arm B).

RESULTS

The trial enrolled 104 patients. After induction, clinical response was 27% with 2% complete responses. Among patients with detectable t(11;14)-positive cells in blood and bone marrow at baseline, four of 20, and one of 14, respectively, became polymerase chain-reaction-negative after induction. Anemia was the only adverse predictor of response in the multivariate analysis. After a median follow-up of 29 months, response rate and duration of response were not significantly different between the two schedules in 61 randomly assigned patients. Median event-free survival (EFS) was 6 months in arm A versus 12 months in arm B; the difference was not significant (P = .1). Prolonged treatment seemed to improve EFS in the subgroup of pretreated patients (5 months in arm A v 11 months in arm B; P = .04). Thirteen percent of patients in arm A and 9% in arm B presented with grade 3 to 4 hematologic toxicity.

CONCLUSION

Single-agent rituximab is active in MCL, but the addition of four single doses at 8-week intervals does not seem to significantly improve response rate, duration of response, or EFS after treatment with the standard schedule.

Antitumor activity of rituximab plus thalidomide in patients with relapsed/refractory mantle cell lymphoma

We evaluated a treatment strategy targeting both lymphoma cells (by rituximab) and the microenvironment (by thalidomide) in 16 patients with relapsed/refractory mantle cell lymphoma (MCL). Rituximab was administered at 375 mg/m2 for 4 weekly doses concomitantly with thalidomide (200 mg daily, with a dose increment to 400 mg on day 15), which was continued as maintenance therapy until progression/relapse. Thirteen patients (81%) experienced an objective response, with 5 complete responders (31%). Median progression-free survival (PFS) was 20.4 months (95% confidence interval [CI], 17.3-23.6 months), and estimated 3-year survival was 75%. In patients achieving a complete response, PFS after rituximab plus thalidomide was longer than PFS after the preceding chemotherapy. Severe adverse events included 2 thromboembolic events and 1 grade IV neutropenia associated with thalidomide. Our results suggest that rituximab plus thalidomide has marked antitumor activity in relapsed/refractory MCL and a low toxicity profile, which warrants further evaluation in MCL.

Results of a phase II multicenter trial of pentostatin and rituximab in patients with low grade B-cell non-Hodgkin's lymphoma: an effective and minimally toxic regimen

This study explored the efficacy and toxicity of the combination of pentostatin and rituximab, effective single agents in low-grade non-Hodgkin's lymphoma (NHL). Sixty patients with previously treated low-grade NHL were enrolled. Except for day 1, both drugs were administered weekly for 4 weeks, with week 5 off. During week 1 (day 1) only rituximab was given; subsequent weekly treatments included both drugs. Patients received a minimum of 2 five-week cycles in order to be evaluable for efficacy. Responses were evaluated on week 5 of cycle 2. If partial response (PR) or stable disease (SD) responses were noted, 2 additional cycles were administered. Final evaluations were done on week 5 of cycle 4. Of 60 patients, 58.3% had an Eastern Cooperative Oncology Group performance status (PS) of 0, and 41.7% had PS of 1; 31.7% and 51.7% had stage III or stage IV disease, respectively. Histology included follicular center, follicular, grade I (45%), II (21.7%), III (1.7%), and small lymphocytic (31.7%). Seventeen patients had prior chemotherapy, but no patients had received prior pentostatin or rituximab. Median age was 60.3 years (range, 32.5-84.7 years). Among 57 evaluable patients, 77% responded (22.3% complete response [CR], 3.5% unconfirmed CR, 35.1% PR, and 10.5% unconfirmed PR); 19.3% had SD, and 8.8% progressive disease (PD). Response rate among previously untreated patients was 83% versus 63% in previously treated patients. Median duration of response was 11 months (range, 2.3-22.2 months); median time to progression was 15 months (range, < 1-25 months). Neutropenia was the only adverse event experienced by >/= 10% of patients. Six deaths were caused by PD, and one death each was caused by acute respiratory distress, possibly related respiratory failure, and cardiac toxicity. These results suggest the combination of pentostatin/rituximab is well tolerated and active in low-grade lymphoma.

Intensive chemotherapy and autologous stem-cell transplantation plus rituximab is superior to conventional chemotherapy for newly diagnosed advanced stage mantle-cell lymphoma: a matched pair analysis

BACKGROUND

The outcome of 20 patients with newly diagnosed mantle-cell lymphoma (MCL) treated on a prospective trial of autologous stem-cell transplantation (ASCT) and rituximab immunotherapy was compared with the outcome of 40 matched historical control patients treated with standard combination chemotherapy.

PATIENTS AND METHODS

Control patients with MCL were identified from a lymphoma database, and pairs were matched with patients receiving ASCT-rituximab for stage of disease, gender and age (+/-5 years). Only patients treated with an anthracycline- or cyclophosphamide-fludarabine-based regimen were included.

RESULTS

Seventeen of 20 patients who received ASCT-rituximab remain alive in remission at a median of 30 months from diagnosis; one patient relapsed 2 years post-ASCT, and two died at 7 and 11 months post-ASCT without evidence of lymphoma. Of 40 patients treated with conventional chemotherapy, with a median follow-up of 80 months, 33 have relapsed or progressed and 29 have died. Overall (OS) and progression-free (PFS) survival were superior in patients treated with ASCT-rituximab compared with those treated with conventional chemotherapy (PFS at 3 years, 89% versus 29%, P <0.00001; OS at 3 years, 88% versus 65%, P = 0.052).

CONCLUSIONS

This matched-pair analysis suggests that patients with advanced-stage MCL treated with ASCT-rituximab had statistically significantly better PFS and a trend toward better OS than patients treated with conventional chemotherapy. Longer follow-up will determine response duration and the true impact of this treatment strategy on PFS and OS.

Innovative strategies in lymphoma therapy

Treatment of malignant non-Hodgkin lymphomas (NHL) in the 21st century has been revolutionized by novel biological agents offering targeted approaches in addition to radio-chemotherapy. Monoclonal antibodies (MoAbs) against lymphatic surface antigens have been effective as monotherapeutic agents, and have already shown their superiority to conventional strategies when combined with chemotherapy. Radioimmunoconjugates are more effective than unlabelled antibodies. Specific inhibitors of neoangiogenesis as well as intracellular signal transduction pathways and antiapoptotic mechanisms have shown their efficacy in phase II studies. Long-term improvement in the setting of minimal residual disease has been observed after vaccination against surface antigens and non-myeloablative allogeneic stem cell transplantation is effective in controlling lymphoma growth. Novel specific antigens are currently identified using expression profiling of lymphomas. In the near future, combinations of biological agents will challenge conventional therapy. These exciting new strategies will improve the success rate in aggressive NHLs and may even challenge the paradigm of incurability of indolent lymphomas.

Treatment of low-grade B-cell lymphoma with the monoclonal antibody rituximab

The anti-CD20 chimeric monoclonal antibody has been a tremendous addition to the therapeutic armamentarium against low-grade lymphoma. In indolent lymphoma, rituximab as a single agent is associated with 50% to 60% objective response rates in the relapsed setting and 60% to 75% as front-line therapy. Chemotherapy plus rituximab combinations have been associated with response rates of 85% to 95% and randomized trials have confirmed a higher response rate for various chemotherapy plus rituximab combinations compared to the same chemotherapy alone. Concurrent chemotherapy with rituximab does not increase toxicity and appears superior to sequences of chemotherapy followed by rituximab. Repeated intermittent therapy is associated with higher response rates and longer duration of remission. When used alone, the activity of rituximab is probably due to a combination of complement-dependent cytotoxicity, antibody-dependent cell-mediated cytotoxicity, and regulatory effects that enhance apoptosis. Dosing could probably be optimized by monitoring serum levels of rituximab in individual patients, because of the tremendous variability in lymphoma tumor burden, rates of tumor proliferation, rates of CD20 antigen production and expression, and clearance of rituximab. Combinations of rituximab with other monoclonal antibodies are currently being tested.

Rituximab: a review of its use in non-Hodgkin's lymphoma and chronic lymphocytic leukaemia

Rituximab is an anti-CD20 monoclonal antibody that has demonstrated efficacy in patients with various lymphoid malignancies, including indolent and aggressive forms of B-cell non-Hodgkin's lymphoma (NHL) and B-cell chronic lymphocytic leukaemia (CLL). While the optimal use of the drug in many clinical settings has yet to be clarified, two pivotal trials have established rituximab as a viable treatment option in patients with relapsed or refractory indolent NHL, and as a standard first-line treatment option when combined with cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) chemotherapy in elderly patients with diffuse large B-cell lymphoma (the most common type of aggressive NHL). The former was a noncomparative trial in relapsed indolent NHL (follicular and small lymphocytic subtypes) with clinical responses achieved in about half of patients treated with rituximab 375 mg/m(2) intravenously once weekly for 4 weeks, which was similar to some of the most encouraging results reported with traditional chemotherapeutic agents. The latter was a randomised comparison of eight cycles of CHOP plus rituximab 375 mg/m(2) intravenously (one dose per cycle) versus CHOP alone in previously untreated elderly patients (60 to 80 years of age) with diffuse large B-cell lymphoma. In this pivotal trial, 2-year event-free and overall survival were significantly higher with rituximab plus CHOP, and there was no increase in clinically significant adverse effects compared with CHOP alone. Treatment with rituximab is generally well tolerated, particularly in terms of adverse haematological effects and serious or opportunistic infections relative to standard chemotherapy. Infusion-related reactions occur in the majority of patients treated with rituximab; these are usually mild to moderate flu-like symptoms that decrease in frequency with subsequent infusions. In approximately 10% of patients, however, severe infusion-related reactions develop (e.g. bronchospasm, hypotension). These reactions are usually reversible with appropriate interventions and supportive care but there have been rare reports of fatalities.

CONCLUSIONS

Clinical trials with rituximab indicate that the drug has broad application to B-cell malignancies, although further clarification is needed to determine its optimal use in many of these clinical settings. Importantly, rituximab in combination with CHOP chemotherapy has emerged as a new treatment standard for previously untreated diffuse large B-cell lymphoma, at least in elderly patients. Compared with conventional chemotherapy, rituximab is associated with markedly reduced haematological events such as severe neutropenia, as well as associated infections. Rituximab may be particularly suitable for elderly patients or those with poor performance status, and its tolerability profile facilitates its use in combination with cytotoxic drugs.

PHARMACODYNAMIC PROPERTIES

Rituximab is a mouse/human chimaeric IgG(1)-kappa monoclonal antibody that targets the CD20 antigen found on the surface of malignant and normal B lymphocytes. Although treatment with rituximab induces lymphopenia in most patients, typically lasting about 6 months, a full recovery of B lymphocytes in the peripheral blood is usually seen 9-12 months after therapy, as CD20 is not expressed on haematopoietic stem cells. CD20 is, however, expressed on >90% of B-cell non-Hodgkin's lymphomas (NHL) and to a lesser degree on B-cell chronic lymphocytic leukaemia (CLL) cells. Although not fully elucidated, the cytotoxic effects of rituximab on CD20-positive malignant B cells appears to involve complement-dependent cytotoxicity, complement-dependent cellular cytotoxicity, antibody-dependent cellular cytotoxicity and induction of apoptosis. In addition, in vitro data indicate that rituximab sensitises tumour cells to the effects of conventional chemotherapeutic drugs.

PHARMACOKINETIC PROPERTIES

Serum rituximab concentrations increased in proportion to dose across a wide range of single- and multiple-dose intravenous regimens in patients with B-cell NHL. When administll NHL. When administered at a dose of 375 mg/m(2) once weekly for 4 weeks in a pivotal trial in patients with relapsed or refractory indolent B-cell NHL (follicular or small lymphocytic subtypes), peak serum concentrations essentially doubled from the first (239.1 mg/L) to the fourth (460.7 mg/L) infusion, while elimination half-life (t(1/2)) increased from 76.3 to 205.8 hours (3.2 to 8.6 days). The concomitant increase in serum rituximab concentrations and t(1/2) with each successive infusion may be due, at least in part, to the elimination of circulating CD20-positive B cells and reduction or saturation of CD20-binding sites after the initial infusions of rituximab. The pharmacokinetic properties of rituximab are also characterised by wide inter-individual variability, and serum drug concentrations that are correlated with clinical response. Although pharmacokinetic data are limited in patients with aggressive forms of NHL, such as diffuse large B-cell lymphoma, rituximab appears to have a similar pharmacokinetic profile in these patients to that in patients with indolent B-cell NHL. The pharmacokinetics of rituximab are also reported to be similar whether the drug is administered with or without cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) chemotherapy.

THERAPEUTIC USE

A number of studies have demonstrated efficacy of intravenous rituximab in patients with various lymphoid malignancies of B-cell origin, including indolent (e.g. follicular lymphoma) and aggressive (e.g. diffuse large B-cell lymphoma) forms of NHL, and CLL, but the drug has not yet been approved for use in CLL, and approved indications in NHL vary between countries. In the US, for example, rituximab is available for the treatment of patients with low-grade or follicular, relapsed or refractory, CD20-positive B-cell NHL. In Europe, the drug has similar approval for relapsed or refractory follicular NHL as in the US, but has also been approved for use in combination with CHOP chemotherapy for the most common aggressive form of NHL (CD20-positive, diffuse large B-cell lymphoma). Rituximab was approved for these indications primarily on the basis of results from two pivotal trials. In Japan, rituximab has been approved for indolent B-cell NHL and mantle cell lymphoma (an aggressive form of B-cell NHL), primarily on the basis of results of a Japanese phase II trial. Indolent NHL: Results of several studies evaluating rituximab 375 mg/m(2) once weekly for 4 weeks in patients with indolent forms of B-cell NHL (primarily follicular and small lymphocytic lymphomas) showed objective response (OR) rates ranging from approximately 40-60% in those receiving the drug for relapsed or refractory indolent B-cell NHL, and slightly higher (50-70%) for those receiving rituximab as first-line therapy. In a pivotal trial in 166 patients with relapsed or refractory low-grade or follicular B-cell NHL, intent-to-treat (ITT) analysis showed an OR rate of 48%, and a projected median time to progression of 13 months. Encouraging data are also emerging on the use of rituximab in combination with chemotherapeutic agents (e.g. CHOP, fludarabine-containing regimens) or other drugs (e.g. interferon-alpha2a) in previously untreated patients with indolent forms of B-cell NHL (primarily follicular and small lymphocytic subtypes). Rates for OR were consistently around 95%, with the majority being complete responses (CRs). Follow-up data from a study in 40 patients with low-grade or follicular B-cell NHL treated with rituximab plus CHOP as first-line therapy showed that responses were durable with a progression-free survival and median duration of response >5 years.Bcl-2 gene rearrangement (t14;18) occurs in malignant cells in up to 85% of patients with follicular lymphoma, and minimal residual disease in peripheral blood and bone marrow can be monitored using polymerase chain reaction (PCR). In several studies assessing blood and/or bone marrow, rituximab has achieved molecular response (conversion from PCR-positive to PCR-negative bcl-2 status) in at least half of the patients. Aggressive NHL: Studies with rituximab as monotherapy in aggressive B-cell NHL, a potentially curable disorder, have generally been restricted to patients with relapsed or recurrent disease, since CHOP has traditionally been the standard first-line treatment regimen. However, promising results from phase II monotherapy studies prompted further clinical investigation of rituximab in conjunction with chemotherapy. Thus, most studies with rituximab in patients with aggressive forms of B-cell NHL have involved combination therapy, including a pivotal randomised trial comparing eight cycles of standard CHOP therapy plus rituximab 375 mg/m(2) (one dose per cycle) versus CHOP alone in 399 previously untreated elderly patients (60-80 years of age) with diffuse large B-cell lymphoma. Results of the pivotal trial showed a clear advantage for rituximab plus CHOP versus CHOP in terms of event-free survival (primary endpoint) at 2 years (57% vs 38%, p < 0.001). Overall survival at 2 years (70% vs 57%, p < 0.01) and CR rate (76% vs 63%, p < 0.01) were also higher with the rituximab-CHOP combination. Other, smaller trials with rituximab in combination with CHOP or other chemotherapeutic regimens, either as first-line therapy or for patients with relapsed or refractory aggressive B-cell NHL, have also shown promising results in terms of clinical response rates.CLL: In relatively small trials (n < 40) conducted primarily in patients with relapsed or refractory B-cell CLL, rituximab monotherapy (various regimens) achieved OR rates of 23-45%, with median duration of response ranging from approximately 3-10 months. (ABSTRACT TRUNCATED)

Delayed-onset neutropenia associated with rituximab therapy

The characteristics of severe neutropenia with a delayed onset following administration of rituximab have been evaluated in 53 consecutively treated patients. All but one patient received rituximab for the treatment of non-Hodgkin's lymphoma. Eight episodes of grade 4 neutropenia were detected between 1 and 5 months after rituximab, when administered alone on five occasions, and on three occasions in combination with chemotherapy, where neutrophil counts had recovered prior to the development of neutropenia. In three episodes, the patients presented with sepsis. Development of neutropenia did not correlate with either the presence of detectable disease or the administration of further treatment. Neutropenia was associated with selective depletion of neutrophil precursors in all but one episode, where it was associated with generalized bone marrow hypoplasia. All episodes developed after a period of either normal or mildly depressed neutrophil counts following treatment with rituximab, and persisted for between several days and several months, before undergoing spontaneous recovery in four instances, and after administration of filgrastim in the remainder. Episodes of neutropenia were associated with disordered immune status manifested by lymphopenia and hypogammaglobulinaemia, raising the possibility that either disturbance of the balance of lymphocyte subsets or an immune dyscrasia induced by rituximab resulted in the development of this type of neutropenia.

Pharmacokinetic study of patients with follicular or mantle cell lymphoma treated with rituximab as 'in vivo purge' and consolidative immunotherapy following autologous stem cell transplantation

BACKGROUND

Little is known about the pharmacokinetics of rituximab in an autologous stem cell transplant (ASCT) setting.

PATIENTS AND METHODS

We evaluated serum rituximab levels in 26 patients with follicular or mantle cell lymphoma treated with a combination of ASCT and immunotherapy. Patients received nine infusions of rituximab (375 mg/m(2)): one dose as an 'in vivo purge' prior to stem cell collection, and two 4-week cycles at 8 and 24 weeks following ASCT. Pre- and post-infusion serum rituximab levels were measured during the purging dose, with doses 1 and 4 of both sets of maintenance rituximab cycles, and 12 weeks and 24 weeks following treatment.

RESULTS

Rituximab levels were detectable after the first infusion, and peaked at a mean concentration of 463.8 micro g/ml after the final dose. Levels remained detectable 24 weeks after completion of treatment. There was a trend toward higher rituximab levels in patients with follicular lymphoma. Serum concentrations achieved during the maintenance cycles were similar to levels observed in patients with measurable lymphoma treated during 'the pivotal trial'. No correlation was observed between serum rituximab levels achieved in the minimal disease state and the risk of later clinical relapse, nor with the ability to achieve a molecular remission following ASCT.

CONCLUSIONS

The finding that patients treated in minimal disease states and at the time of active disease both achieve similar final serum rituximab concentrations after four infusions suggests that the pharmacokinetics are complex, and may not necessarily correlate with disease burden. The precise factors influencing rituximab clearance in patients with lymphoma are unresolved, and this remains an area of active research.

An overview of the current clinical use of the anti-CD20 monoclonal antibody rituximab

The chimeric anti-CD20 monoclonal antibody rituximab has become part of the standard therapy for patients with non-Hodgkin's lymphoma (NHL). To date, more than 300 000 patients have been treated with rituximab worldwide, including patients with indolent and aggressive NHL, Hodgkin's disease and other B-cell malignancies. Combination of rituximab with cytotoxic agents or cytokines has been explored in a number of different studies. Rituximab is now also approved for patients with diffuse large B-cell lymphoma when combined with standard CHOP chemotherapy (cyclophosphamide, doxorubicin, vincristine and prednisone). The monoclonal antibody is generally well tolerated. Most adverse events are infusion-associated, including chills, fever and rigor related to the release of cytokines.

Rituximab: enhancing outcome of autologous stem cell transplantation in non-Hodgkin's lymphoma

High-dose chemotherapy and autologous stem cell transplantation (ASCT) is a potentially curative therapy for younger patients with relapsed aggressive non-Hodgkin's lymphoma, and is under investigation as first-line treatment and as therapy for indolent and mantle cell non-Hodgkin's lymphoma. However, between 40% and 70% of all patients relapse after ASCT because of contamination of the stem cell product or persistence of residual tumor cells. Evidence is emerging that the administration of rituximab as an in vivo purging agent before ASCT is effective in eliminating lymphoma cell contamination, as measured by clearance of bcl-2-positive cells from stem cell harvests. Furthermore, in vivo purging with rituximab does not adversely affect the stem cell yield or function. Maintenance therapy with rituximab post-transplantation has also been explored as a means of eliminating residual tumor cells. Results suggest that rituximab may eradicate minimal residual disease post-transplant and help prevent relapse. The efficacy of both in vivo purging and maintenance therapy with rituximab is currently being investigated in a large, multicenter, randomized trial by the European Group for Blood and Bone Marrow Transplantation in patients with follicular non-Hodgkin's lymphoma. Results from this and other ongoing trials will confirm the full potential of rituximab in ASCT.

Cell surface antigen and molecular targeting in the treatment of hematologic malignancies

Conventional cytotoxic therapy of hematologic malignancies is often associated with significant morbidity. This morbidity is often due to the lack of specificity for hematopoietic cells. Therefore, the concept of targeted therapy for patients with hematologic malignancies has received attention for many years. The goal of monoclonal antibody therapy is to target specific cell surface antigens on malignant hematopoietic cells, while sparing normal cells and tissues. Currently, monoclonal antibodies are being evaluated for their cytotoxic effects as well as their ability to deliver toxic agents or radiation. Rituximab, a chimeric anti-CD20 antibody, has shown response rates of approximately 50% with minimal toxicity in patients with refractory indolent lymphoma. Campath-1H (anti-CD52) has shown encouraging results in patients previously treated for chronic lymphocytic leukemia, with response rates up to 33%, although with significant toxicity. Anti-CD33 antibodies are being used to deliver cytotoxic agents, such as calicheamicin to patients with acute myeloid leukemia with response rates up to 30%. In addition, anti-CD33 and anti-CD45 antibodies have been used to deliver radiation directly to leukemic cells. (131)I-labeled anti-CD45 antibodies are being studied in combination with conventional preparative regimens in patients receiving bone marrow transplantation. Lastly, the therapeutic agent STI571 (signal transduction inhibitor 571) has demonstrated the capability of targeting specific molecular abnormalities seen in hematologic malignancies. STI571 targets the tyrosine kinase activity of the bcr-abl fusion protein seen in chronic myeloid leukemia. STI571 has induced complete hematologic responses in up to 98% of patients evaluated in clinical trials.

Mantle cell lymphoma: new treatments targeted to the biology

Mantle cell lymphoma (MCL) represents a distinct lymphoma subtype. The prognosis of patients with MCL is the poorest among lymphoma patients and the response to conventional treatments is inadequate. New approaches targeted to the biology of MCL and the genetics underlying the disease are being studied. Monoclonal antibodies directed at molecules expressed on MCL cells are already used in the clinical setting. This article reviews the literature on these and other new possible treatment modalities.

Immunotherapy with rituximab following high-dose therapy and autologous stem-cell transplantation for mantle cell lymphoma

Advanced-stage mantle cell lymphoma (MCL) is a disease for which no curative treatment strategy exists. Results with standard combination chemotherapy, with or without an anthracycline, are disappointing, and new and better therapies are needed. High-dose therapy and autologous stem-cell transplantation (ASCT) have been performed in patients with MCL both up front and at relapse with varying degrees of success. Rituximab (Rituxan; Genentech, Inc, South San Francisco, CA, and IDEC Pharmaceuticals, San Diego, CA) has shown moderate response rates in patients with MCL. It has also been used safely and effectively as an in vivo purge during ASCT for patients with lymphoma. We are currently investigating an aggressive protocol in patients with newly diagnosed, untreated MCL using a combination of two promising therapeutic modalities, high-dose therapy-ASCT and rituximab. Since 1999, 13 patients with newly diagnosed MCL have been enrolled in this phase II clinical trial. CHOP (cyclophosphamide/prednisone/vincristine/doxorubicin) is used as debulking chemotherapy. Stem cells are mobilized with 5 days of granulocyte colony-stimulating factor 10 μg/kg/d, with a single infusion of rituximab 375 mg/m² used as an in vivo purge before stem-cell collection by large-volume leukapheresis. The transplant conditioning regimen is cyclophosphamide/carmustine/etoposide. Post-transplant consolidative immunotherapy consists of rituximab 375 mg/m², administered as two 4-week cycles at 2 and 6 months post-transplant. So far, 12 patients (7 men/5 women) with a median age of 55 years (range, 41 to 65 years) have been transplanted. Patients were first assessed and then transplanted a median of 40 and 201 days, respectively, from diagnosis. International Prognostic Index at diagnosis was low (n = 3), low-intermediate (n = 8), and high-intermediate (n = 1). A median of six cycles of CHOP was required to debulk tumor sufficiently for transplant. Response to CHOP was 100% with six complete responses, one complete response unconfirmed, and five partial responses. Transplantation was well tolerated. Patients engrafted quickly, with a median of 11.5 days to neutrophil engraftment and 10 days to platelet independence. Patients had modest transfusion requirements, requiring a median of four units of packed red blood cells and two and a half platelet transfusions. Six to 8 weeks post-transplant, six patients were in complete response, four in complete response unconfirmed, and two in partial response. Eight patients have received all eight maintenance rituximab treatments, and four have received only their first cycle. Following rituximab, the two patients in partial response and two in complete response unconfirmed converted to complete response. With a median follow-up of 239 days from transplant (range, 61 to 727 days), all patients remain alive and well with no documented relapses. Samples for molecular monitoring have been drawn from the stem-cell graft, and serially from the peripheral blood and bone marrow of patients at baseline, preapheresis, pretransplant, and post-transplant at 3-month intervals. This data shows that ASCT followed by rituximab immunotherapy is feasible and safe in patients with MCL. Although patient numbers are low and follow-up time is short, preliminary results are encouraging. Rituximab may convert partial responders to complete responders. The durability of responses will be determined with longer follow-up. Semin Oncol 29 (suppl 2):56-69. Copyright © 2002 by W.B. Saunders Company.

Monoclonal antibody therapy in lymphoid malignancies

The concept of targeted therapy for patients with advanced cancer has intrigued researchers for many years. The lymphoid malignancies are particularly good candidates for this therapeutic approach, due to the identification of multiple lymphocyte-specific antigens. The recent introduction of rituximab marks the beginning of a new era in the treatment of lymphoid malignancies. Rituximab is one of the most active single agents for patients with refractory indolent lymphoma, producing response rates of approximately 50%, with low toxicity and a brief duration of treatment. Additional uses of rituximab are being evaluated in ongoing clinical trials, and are briefly reviewed. As a first-line agent, responses of approximately 70% are produced in patients with indolent lymphoma, with minimal toxicity. A substantial percentage of patients can be successfully retreated with rituximab, with second remission durations longer than the first remission (14-16 months versus 12 months). Multiple combination regimens using rituximab plus chemotherapy are also being evaluated. Although the role of these combined approaches is incompletely defined, high complete response rates can be obtained, with a higher rate of molecular complete remission (i.e., eradication of detectable bcl-2 rearrangements) than has been observed in patients receiving chemotherapy alone. Rituximab is also being evaluated in other CD20(+) lymphoid malignancies including large-cell lymphoma, chronic lymphocytic leukemia, mantle cell lymphoma, and Waldenstrom's macroglobulinemia. Within the next 12 months, several additional monoclonal antibodies will be available for the treatment of lymphoid malignancies. These include the radioimmunoconjugates tositumomab (Bexxar) and ibritumomab (Zevalin), as well as Campath-1H (anti-CD52) monoclonal antibody. Early clinical data with each of these agents are also briefly reviewed.