Platinum and high-dose cytarabine-based regimens are efficient in ultra high/high-risk chronic lymphocytic leukemia and Richter's syndrome: results of a French retrospective multicenter study

Venetoclax plus dose-adjusted R-EPOCH (VR-DA-EPOCH) or G-EPOCH bridging to subsequent cellular therapy for the patients with transformed lymphoma a single center clinical experience

Indolent lymphoma, including chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and follicular lymphoma (FL), can undergo histological transformation into an aggressive subtype, typically diffuse large B-cell lymphoma (DLBCL). The prognosis of transformed lymphoma is poor. In this study, we reported the efficacy and toxicity of a combination of venetoclax, dose-adjusted rituximab or obinutuzumab, etoposide, prednisone, vincristine, doxorubicin, and cyclophosphamide (VR-DA-EPOCH or VG-DA-EPOCH) in 11 patients with biopsy-proven histology transformation into DLBCL, including 8 patients with RT and 3 with transformed FL (tFL). The study was conducted between October 2019 and March 2023 at our single center. The median age of participants at enrolment was 53 years. Six patients (85.7%, 6/7) achieved complete remission (CR) at the end of treatment. The best overall response rate (ORR) and CR rate were both 72.7%, respectively. Two patients received autologous hemopoietic stem cell transplant (ASCT) while two patients received ASCT concurrently with CAR-T therapy for consolidation. With a median follow-up of 13.5 (range, 2.4-29.8) months after enrollment, the median event-free survival, progression-free survival, and overall survival were 9.4, 11.5, and 17.5 months, respectively. Hematologic toxicities of grade ≥3 consisted of neutropenia (90.9%, 10/11), thrombocytopenia (63.6%, 7/11), and febrile neutropenia (54.5%, 6/11). In conclusion, VR-DA-EPOCH or VG-DA-EPOCH was a promising strategy to achieve an early remission, bridging to cellular therapy within this population.

Richter's transformation: Transforming the clinical landscape

Richter transformation (RT) represents an aggressive histological transformation from chronic lymphocytic leukaemia, most often to a large B cell lymphoma. It is characterised by chemo-resistance and subsequent short survival. Drug development has struggled over recent years in light of the aggressive kinetics of the disease, lack of pivotal registrational trials and relative rarity of the phenomenon. In this review we will highlight the diagnostic and therapeutic challenges of managing patients with RT as well as taking a look to the future therapeutic landscape. Highly active therapies developed across B cell malignancies are starting to impact this field, with T-cell activation therapies (CAR-T, bispecific antibodies), antibody-drug conjugates, and novel small molecule inhibitor combinations (e.g. BTKi-BCL2i) being actively studied. We will highlight the data supporting these developments and look to the studies to come to provide hope for patients suffering from this devastating disease.

From genetics to therapy: Unraveling the complexities of Richter transformation in chronic lymphocytic leukemia

Richter transformation (RT) refers to the progression of chronic lymphocytic leukemia, the most prevalent leukemia among adults, into a highly aggressive lymphoproliferative disorder, primarily a diffuse large B-cell lymphoma. This is a severe complication that continues to be a therapeutic challenge and remains an unmet medical need. Over the last five years, significant advances have occurred in uncovering the biological processes leading to the RT, refining criteria for properly diagnose RT from other entities, and exploring new therapeutic options beyond the ineffective chemotherapy. This review summarizes current knowledge in RT, including recent advances in the understanding of the pathogenesis of RT, in the classification of RT, and in the development of novel therapeutic strategies for this grave complication.

SOHO State of the Art Updates and Next Questions | Treatment of Richter's Transformation

Richter's transformation (RT) is a rare condition, represented by the development of an aggressive lymphoma arising from underlying chronic lymphocytic leukemia/small lymphocytic lymphoma. The management of RT remains challenging, necessitating combined therapeutic strategies to achieve favorable outcomes. Traditional treatment options for RT have involved intensive chemotherapy regimens, often with limited success due to the high-risk nature of the disease. However, recent advances in the understanding of RT pathogenesis have led to the emergence of novel targeted therapies that show promising results. Noncovalent Bruton tyrosine kinase inhibitors, T-cell-engaging bispecific antibodies, chimeric antigen receptor T-cells, and conjugated monoclonal antibodies may hold promise for improved outcomes in RT, especially when combined in a multitargeted fashion. Further prospective randomized trials and collaborative efforts are warranted to optimize treatment algorithm and ultimately improve patient outcomes in this dismal condition. This review provides a comprehensive overview of the current treatment options for RT.

Richter Transformation of Chronic Lymphocytic Leukemia-Are We Making Progress?

PURPOSE OF REVIEW

The treatment paradigm of chronic lymphocytic leukemia (CLL) has dramatically changed with the advent of novel targeted agents over the past decade. Richter transformation (RT), or the development of an aggressive lymphoma from a background of CLL, is a well-recognized complication of CLL and carries significantly poor clinical outcomes. Here, we provide an update on current diagnostics, prognostication, and contemporary treatment of RT.

RECENT FINDINGS

Several genetic, biologic, and laboratory markers have been proposed as candidate risk factors for the development of RT. Although a diagnosis of RT is typically suspected based on clinical and laboratory findings, tissue biopsy is essential for histopathologic confirmation of diagnosis. The standard of care for RT treatment at this time remains chemoimmunotherapy with the goal of proceeding to allogeneic stem cell transplantation in eligible patients. Several newer treatment modalities are being studied for use in the management of RT, including small molecules, immunotherapy, bispecific antibodies, and chimeric antigen receptor T-cell (CAR-T) therapy. The management of patients with RT remains a challenge. Ongoing trials show enormous promise for newer classes of therapy in RT, with the hope being that these agents can synergize, and perhaps supersede, the current standard of care in the near future.

Accelerated Chronic Lymphocytic Leukemia and Richter Transformation in the Era of Novel Agents

BACKGROUND

Tremendous developments in the field of chronic lymphocytic leukemia (CLL) in recent years have led to a revolutionary change in the treatment approach, which today is based on targeted treatments with a good response and optimal prognosis. Nevertheless, CLL can present or progress to "accelerated CLL" (A-CLL) or to "Richter transformation" (RT) and these two entities have a more aggressive course and are still characterized by challenges in the fields of diagnosis and therapy. In the current review, we summarized the latest knowledge in terms of diagnostic approaches to A-CLL, available treatments and clinical trials, for both A-CLL and RT which still pose an unmet need and require additional basic and clinical investigations.

SUMMARY

A-CLL is a rare and underdiagnosed entity that probably stands in the "gray zone" between CLL and RT, generally holding an intermediate prognosis. Its diagnosis is mainly based on histological findings including expanded proliferation centers, increased mitotic activity, and/or high Ki-67 index. Due to its rarity, its treatment approach has still not been defined, but it seems that novel agents, especially Bruton tyrosine kinase inhibitors (BTKi), are effective. As for RT, the standard therapy still consists of chemo-immunotherapy followed by stem-cell transplantation for fit responders with a dismal prognosis. New approaches are recently adopted including B-cell inhibition via novel agents (BTKi, venetoclax), T-cell engagers (checkpoint inhibitors, bispecific antibodies [BiTe] or the chimeric antigen receptor [CAR] technology), antibody-drug conjugates, or drug combinations. Although both CAR-T and BiTe seem promising, especially when combined with BTKi, evidence is still insufficient, and patients should generally be recruited in clinical trials.

KEY MESSAGES

The field of CLL has been a subject of major advances in recent years, but A-CLL and RT remain topics of "unmet need" and require further studies to identify the best diagnostic approach and a more effective treatment.

A phase 2 study of nivolumab combined with ibrutinib in patients with diffuse large B-cell Richter transformation of CLL

Richter transformation (RT) is a rare complication of chronic lymphocytic leukemia (CLL) that has dismal outcomes. Upregulation of PD-1/PD-L1 drives immunological evasion in patients with RT. We hypothesized that combining nivolumab, a PD-1 blocking antibody, with the BTK inhibitor (BTKi) ibrutinib could potentiate tumor-cell killing. We conducted an investigator-initiated phase 2 clinical trial to assess the efficacy of combined nivolumab and ibrutinib in patients with diffuse large B-cell lymphoma (DLBCL) RT and CLL. Patients included were ≥18 years of age with adequate hepatic and renal function. Patients received nivolumab every 2 weeks of a 4-week cycle for a maximum of 24 cycles. A standard dose ibrutinib was initiated from cycle 2 onward and continued daily until progression. For patients who were already on ibrutinib at the time of study entry, the same was continued while nivolumab was initiated. A total of 24 patients with RT with a median age of 64.5 years (range, 47-88) were enrolled. Ten patients (42%) had received prior treatment for RT and 13 patients (54%) had received a prior BTKi. A total of 10 patients (42%) responded with a median duration of response of 15 months. The median overall survival was 13 months. Four of 24 (17%) patients had checkpoint inhibition-related immunological toxicities. In the CLL cohort, 10 patients were enrolled, of whom 3 patients converted from partial to complete remission; 1 patient had a grade 2 immunological toxicity. Combined nivolumab and ibrutinib is an active regimen for patients with DLBCL RT with an overall response rate of 42%. Given the limited treatment options for patients with RT, checkpoint inhibition provides a potential therapeutic option. This trial is registered at www.clinicaltrials.gov as #NCT02420912.

Immunological Aspects of Richter Syndrome: From Immune Dysfunction to Immunotherapy

Richter Syndrome (RS) is defined as the development of an aggressive lymphoma in patients with a previous or simultaneous diagnosis of chronic lymphocytic leukemia (CLL). Two pathological variants of RS are recognized: diffuse large B-cell lymphoma (DLBCL)-type and Hodgkin lymphoma (HL)-type RS. Different molecular mechanisms may explain the pathogenesis of DLBCL-type RS, including genetic lesions, modifications of immune regulators, and B cell receptor (BCR) pathway hyperactivation. Limited data are available for HL-type RS, and its development has been reported to be similar to de novo HL. In this review, we focus on the immune-related pathogenesis and immune system dysfunction of RS, which are linked to BCR over-reactivity, altered function of the immune system due to the underlying CLL, and specific features of the RS tumor microenvironment. The standard of care of this disease consists in chemoimmunotherapy, eventually followed by stem cell transplantation, but limited possibilities are offered to chemo-resistant patients, who represent the majority of RS cases. In order to address this unmet clinical need, several immunotherapeutic approaches have been developed, namely T cell engagement obtained with bispecific antibodies, PD-1/PD-L1 immune checkpoint blockade by the use of monoclonal antibodies, selective drug delivery with antibody-drug conjugates, and targeting malignant cells with anti-CD19 chimeric antigen receptor-T cells.

Emerging Therapies for the Management of Richter Transformation

Richter transformation (RT) refers to the development of an aggressive lymphoma in patients with underlying chronic lymphocytic leukemia/small lymphocytic lymphoma. Aside from a small subgroup of patients with clonally unrelated and previously untreated chronic lymphocytic leukemia, the disease responds poorly to standard therapies and prognosis is dismal. Recent developments in the understanding of the biology of RT and the advent of several targeted agents may result in improved outcomes for these patients. The purpose of this review is to analyze recent data on the pathogenesis and treatment of RT. We reviewed studies addressing the pathophysiology of RT and analyzed the data for frontline chemoimmunotherapy and emerging targeted therapies likely to play a significant role in the future management of RT. Several biologic and clinical factors may help identify those who are unlikely to respond to conventional chemoimmunotherapy; where possible, these patients should be managed with a novel approach. Emerging therapies for the management of RT include chimeric antigen receptor T-cell therapy, noncovalent Bruton tyrosine kinase inhibitors, and T-cell-engaging bispecific antibodies. The use of less toxic and more effective targeted therapies may result in improved outcomes. Larger, prospective clinical trials are required to confirm efficacy and safety of novel agents for the management of RT, particularly when used in combination with other targeted therapies and in addition to chemoimmunotherapy regimens.

Practical Management of Richter Transformation in 2023 and Beyond

While the past decade has witnessed unprecedented progress for patients with chronic lymphocytic leukemia (CLL), outcomes for patients with Richter transformation (RT) remain dismal. Multiagent chemoimmunotherapy regimens, such as rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone, are commonly used, although outcomes are far poorer than observed with the same regimens used in de novo diffuse large B-cell lymphoma. The revolutionary targeted therapies approved for CLL, such as inhibitors of Bruton tyrosine kinase and B-cell leukemia/lymphoma-2, have limited activity in RT as monotherapy, and initial promising activity of checkpoint blockade antibodies was also eventually found to be ineffective as monotherapy for most patients. Over the past few years, as outcomes for patients with CLL improved, there has been a growing focus of the research community on improving our biological understanding of the underlying pathophysiology of RT and on translating these new insights into rational combination strategies that are poised to improve therapeutic outcomes. Here, we present a brief overview of the biology and diagnosis of RT, as well as prognostic considerations, before providing a summary of the data supporting various therapies that have been recently studied in RT. We then turn our attention to the horizon and describe several of the promising novel approaches under investigation to treat this challenging disease.

Obinutuzumab, High-Dose Methylprednisolone (HDMP), and Lenalidomide for the Treatment of Patients with Richter's Syndrome

Background: For patients with Richter's Syndrome (RS), a durable response is rarely achieved with standard therapies. Significant efforts have focused on the development of novel treatments with reduced toxicity. We describe our experience using the novel combination of obinutuzumab, high-dose methylprednisolone (HDMP) and lenalidomide (len) in patients with RS. Patients and Methods: Eligible patients included adults with biopsy-proven RS. Patients received obinutuzumab 1000 mg × 8 doses. All patients received HDMP 1000 mg/m² on days 1-5 of cycles 1-4. Patients were administered len PO daily, starting at a dose of 5 mg. Starting on C2D1, the dose increased every 2 weeks in 5 mg increments to a maximum of 25 mg PO daily. Results: Seven patients were treated. The median dose of len was 10 mg and the median number of cycles of treatment completed was 2. The most common grade 3/4 adverse events were neutropenia (29%) and pulmonary embolism (29%). The overall response rate for the entire cohort was 43% (95% CI, 10-82%). All patients who achieved a response underwent consolidative autologous or allogeneic stem cell transplant and remain in remission to date. Conclusions: The combination of obinutuzumab, HDMP, and len is a well-tolerated, outpatient regimen that could serve as a bridge to transplantation, or as palliation for transplant-ineligible patients with RS.

Richter's Transformation

PURPOSE OF REVIEW

Richter's transformation (RT) occurs when chronic (CLL) transforms into an aggressive lymphoma. Despite improvements in the treatment of CLL, prognosis for RT remains poor. Here, we review current literature of RT, with a focus on novel treatment options.

RECENT FINDINGS

Efforts are underway to improve outcomes for patients with RT. While small molecule inhibitors have limited efficacy as monotherapy, recent developments combining them with chemo-immunotherapy show promise. Studies exploring the use of cellular therapies including chimeric antigen receptor T-cells and bispecific antibodies are ongoing. The current treatment paradigm for RT is to enroll these patients on a clinical trial when available, together with consultation for a consolidative allogeneic stem cell transplant. Trials investigating novel combinations and cellular therapy are ongoing. Determining predictive variables of transformation is imperative to design studies that allow for early identification and intervention for patients with RT.

Richter Transformation in Chronic Lymphocytic Leukemia: Update in the Era of Novel Agents

Richter transformation (RT) is a poorly understood complication of chronic lymphocytic leukemia (CLL) with a dismal prognosis. It is associated with a switch in histopathology and biology, generally with a transformation of the original CLL clone to diffuse large B-cell lymphoma (DLBCL) or less frequently to Hodgkin's variant of Richter transformation (HVRT). It occurs in 2-10% of CLL patients, with an incidence rate of 0.5-1% per year, and may develop in treatment-naïve patients, although it is more common following therapy. In recent years, there has been a deeper understanding of the molecular pathogenesis of RT that involves the inactivation of the TP53 tumor suppressor gene in 50-60% of cases and the activation of aberrations of NOTCH1 and MYC pathways in about 30% of cases. Compared to the preceding CLL, 80% of cases with DLBCL-RT and 30% of HVRT harbor the same IGHV-D-J rearrangements, indicating a clonal evolution of the disease, while the remaining cases represent de novo lymphomas that are clonally unrelated. Despite advances in understanding the molecular variations and the pathogenesis of the disease, there is still no significant improvement in patient outcomes. However, if no clinical trials were designed for patients with RT in the past, now there many studies for these patients that incorporate new drugs and novel combinations that are being explored. In this review, we summarize the new information accumulated on RT with special emphasis on results involving the novel therapy tested for this entity, which represents an unmet clinical need.

[Richter Syndrome: Diagnostic and Therapeutic Management]

Richter syndrome (RS) is defined as the occurrence of an aggressive lymphoma, most commonly diffuse large B-cell lymphoma (DLBCL) and rarely Hodgkin lymphoma (HL), in a patient with prior or concomitant chronic lymphocytic leukemia (CLL). RS is estimated to occur in 0.5-1 % per year and is associated with adverse outcome. In the vast majority of patients (80 %), RS is clonally related to the prior CLL. Those with unrelated RS appear to have better outcome. The therapeutic approach is based on those of de novo DLBCL or HL. However, even with modern immunochemotherapy regimens, response rate remains low. In eligible patients with related RS, a consolidation by autologous or allogeneic stem-cell transplantation must be proposed. Combinations including therapies targeting BCR or BCL2 and effective in CLL are currently being evaluated in RS. Novels immunotherapies could be promising approaches based on preliminary results.

Revisiting Richter transformation in the era of novel CLL agents

Richter transformation (RT) is the development of aggressive lymphoma - most frequently diffuse large B-cell lymphoma (DLBCL) and rarely Hodgkin lymphoma (HL) - arising on the background of chronic lymphocytic leukaemia (CLL). Despite recent advances in CLL treatment, RT also develops in patients on novel agents, usually occurring as an early event. RT incidence is lower in CLL patients treated with novel agents in the front line compared to relapsed/refractory cases, with a higher incidence in patients with TP53 disruption. The genetic heterogeneity and complexity are higher in RT-DLBCL than CLL; the genetics of RT-HL are largely unknown. In addition to TP53, aberrations in CDKN2A, MYC, and NOTCH1 are common in RT-DLBCL; however, no distinct RT-specific genetic aberration is recognised yet. RT-DLBCL on ibrutinib is frequently associated with BTK and PLCG2 mutations. Here, we update on genetic analysis, diagnostics and treatment options in RT in the era of novel agents.

Diagnosis and Treatment of Chronic Lymphocytic Leukemia: Recommendations of the French CLL Study Group (FILO)

As a result of significant recent developments, the management of patients with chronic lymphocytic leukemia (CLL) is changing, and new therapeutic options will continue to emerge in the near future. The recommendations of the French Innovative Leukemia Organization (FILO-CLL) group presented here are intended to provide practical recommendations for physicians taking care of CLL patients, taking into account the availability of both biological tests and therapies in daily practice in France at the time of publication. This text details the documented information and guidelines on diagnosis, indications for treatment, infectious complications and therapeutic strategies in frontline and relapsed CLL as well as in particular conditions such as autoimmune cytopenia or Richter syndrome.

Clinical characteristics and outcomes of Richter transformation: experience of 204 patients from a single center

The natural history, prognostication and optimal treatment of Richter transformation developed from chronic lymphocytic leukemia (CLL) are not well defined. We report the clinical characteristics and outcomes of a large series of biopsy-confirmed Richter transformation (diffuse large B-cell lymphoma or high grade B-cell lymphoma, n=204) cases diagnosed from 1993 to 2018. After a median follow up of 67.0 months, the median overall survival (OS) was 12.0 months. Patients who received no prior treatment for CLL had significantly better OS (median 46.3 vs. 7.8 months; P<0.001). Patients with elevated lactate dehydrogenase (median 6.2 vs. 39.9 months; P<0.0001) or TP53 disruption (median 8.3 vs. 12.8 months; P=0.046) had worse OS than those without. Immunoglobulin heavy chain variable region gene mutation, cell of origin, Myc/Bcl-2 double expression and MYC/BCL2/BCL6 double-/triple-hit status were not associated with OS. In multivariable Cox regression, elevated lactate dehydrogenase [Hazard ratio (HR) 2.3, 95% Confidence Interval (CI): 1.3-4.1; P=0.01], prior CLL treatment (HR 2.0, 95%CI: 1.2-3.5; P=0.01), and older age (HR 1.03, 95%CI: 1.01-1.05; P=0.01) were associated with worse OS. Twenty-four (12%) patients underwent stem cell transplant (20 autologous and 4 allogeneic), and had a median post-transplant survival of 55.4 months. In conclusion, the overall outcome of Richter transformation is poor. Richter transformation developed in patients with untreated CLL has significantly better survival. Stem cell transplant may benefit select patients.

The clinical study on treatment of CD19-directed chimeric antigen receptor-modified T cells in a case of refractory Richter syndrome

Richter syndrome (RS) indicates the transformation of chronic lymphocytic leukemia (CLL) into an aggressive lymphoma (mostly DLBCL). Richter syndrome is a rare complication with an aggressive clinical course, bearing an unfavorable prognosis. Currently, there is no effective treatment for it. As a novel cellular‐based immune therapy, chimeric antigen receptor‐modified T (CART) cells treatment is gradually used in treating hematological malignancies, especially in CD19⁺ B‐cell malignancy. Therefore, CD19‐directed chimeric antigen receptor‐modified T cells (CART‐19) treatment is promising to be used as a new method for RS patients. In our study, one RS patient expressing high level of CD19 molecule was enrolled in clinical trial; he has received a series of treatments but did not achieve a satisfactory therapeutic effect. The patient totally received 3.55 × 10⁸ autologous CART‐19 cells infusion. After CART‐19 infusion, the mainly clinical side effect was repeated fever. The maximal duration period was 24 days and the highest temperature was 40.1°C. Pancytopenia and significantly serum cytokines level rise were observed, including IFN‐γ, IL‐6, and IL‐10. Before discharge, the level of cytokines reduced to normal levels. In addition, we detected the serum biochemical indices as like K⁺, Ca²⁺, creatinine, and glutamic‐pyruvic transaminase, all of these indices were normal. This showed that there was no tumor necrosis syndrome after treatment. The proportion of B cells in patient's peripheral blood decreased from 72% to 40.2% after infusion, co‐occurring with reduction in lymph nodes and hematopoietic reconstitution. Based on the recent revolution in the therapeutic landscape for hematological malignancies including B‐cell lymphomas, CART‐CD19 cell therapy as a new therapeutic option for RS might be available in the coming years. It aims to reduce patient's tumor burden, prolong their survival time, and provide opportunities for other sequential therapy such as chemotherapy and bone marrow transplantation.

Immunochemotherapy for Richter syndrome: current insights

Richter syndrome (RS) is recognized as the development of a secondary and aggressive lymphoma during the clinical course of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). Most of such histological transformations are from RS to diffuse large B-cell lymphoma (DLBCL-RS, 90%) and Hodgkin’s lymphoma (HL-RS, 10%). Histopathological examination is a prerequisite for diagnosis. It is crucial to assess the relationship between the RS clone and the underlying CLL/SLL because clonally related DLBCL-RS has a poor outcome, while clonally unrelated cases have a prognosis similar to de novo DLBCL. An anti-CD20 antibody-based immunochemotherapy is hitherto the frontline treatment of choice for DLBCL-RS; nonetheless, the results are unsatisfactory. Allogeneic stem cell transplantation should be offered to younger and fit patients as a consolidative treatment; however, the majority of the patients may not be qualified for this procedure. The HL-RS transformation has better outcomes than those of DLBCL-RS and can effectively be treated by the adriamycin, bleomycin, vinblastine, and dacarbazine regimen. Although novel agents are currently being investigated for RS, immunochemotherapy nevertheless remains a standard treatment for DLBCL-RS.

Richter transformation in the era of novel agents

Recent approvals of several oral targeted agents have revolutionized chronic lymphocytic leukemia (CLL) therapy. However, CLL patients continue to progress; particularly, 4% to 20% of previously treated CLL patients undergo transformation into high-grade lymphoma. Richter transformation is defined as a transformation of CLL into aggressive lymphoma, most commonly diffuse large B-cell lymphoma. These patients typically have poor response to traditional chemotherapy used to treat de novo diffuse large B-cell lymphoma and similar or shorter overall survival (median 3-11 months) in the era of novel agents. Here, I review the contemporary literature on Richter transformation, particularly in the context of novel agents used in CLL, and discuss the management approach for these patients.

An update in treating transformed lymphoma

Indolent lymphomas typically have a prolonged course and favorable prognosis. Recent data support survival times that can reach several decades, even if periodic treatment is needed to manage symptoms or stabilize disease. However, all indolent lymphomas have the potential to undergo transformation to an aggressive phenotype, clinically characterized by a rapid progression of adenopathy, new-onset constitutional symptoms, or laboratory abnormalities, and the immediate need for therapeutic intervention. The most common scenario is transformation of follicular lymphoma to either diffuse large B-cell lymphoma or high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 translocations; however, other indolent subtypes such as marginal zone lymphoma, lymphoplasmacytic lymphoma, small lymphocytic lymphoma/chronic lymphocytic leukemia, or even nodular lymphocyte predominant Hodgkin lymphoma, can undergo similar histologic transformation. The prognosis of transformed lymphomas has historically been quite poor, but there is ample evidence this is changing in the rituximab era. This article will provide a review of transformed lymphomas with an emphasis on treatment and the nuances of diagnosis and clinical management. Unless otherwise specified, all discussion in this review pertains to transformed follicular lymphoma which is the more common scenario and the subtype with the most robust data. In many cases, this information can be extrapolated and applied to other indolent histologies (i.e. transformed marginal zone lymphoma); however, several other clinical scenarios, such as Richter's transformation and "double hit" transformations, warrant a distinct discussion and will be reviewed separately.

Biology and treatment of Richter syndrome

Richter syndrome (RS) is the development of an aggressive lymphoma in patients with chronic lymphocytic leukemia (CLL). Two pathologic variants of RS are recognized: namely, the diffuse large B-cell lymphoma (DLBCL) variant and the rare Hodgkin lymphoma (HL) variant. Histologic documentation is mandatory to diagnose RS. The clinical suspicion of RS should be based on clinical signs and symptoms. Differential diagnosis between CLL progression and RS and choice of the biopsy site may take advantage of positron emission tomography/computed tomography. Molecular lesions of regulators of proliferation (CDKN2A, NOTCH1, MYC) and apoptosis (TP53) overall associate with ∼90% of DLBCL-type RS, whereas the biology of the HL-type RS is largely unknown. The prognosis of the DLBCL-type RS is unfavorable; the outcome of HL-type RS appears to be better. The most important RS prognostic factor is the clonal relationship between the CLL and the aggressive lymphoma clones, with clonally unrelated RS having a better prognosis. Rituximab-containing combination chemotherapy for DLBCL is the most widely used treatment in DLBCL-type RS. Fit patients who respond to induction therapy should be offered stem cell transplantation (SCT) to prolong survival. Adriamycin, bleomycin, vinblastine, and dacarbazine is the preferred regimen for the HL-type RS, and SCT consolidation is less used in this condition.

Chk1 inhibition significantly potentiates activity of nucleoside analogs in TP53-mutated B-lymphoid cells

Treatment options for TP53-mutated lymphoid tumors are very limited. In experimental models, TP53-mutated lymphomas were sensitive to direct inhibition of checkpoint kinase 1 (Chk1), a pivotal regulator of replication. We initially tested the potential of the highly specific Chk1 inhibitor SCH900776 to synergize with nucleoside analogs (NAs) fludarabine, cytarabine and gemcitabine in cell lines derived from B-cell malignancies. In p53-proficient NALM-6 cells, SCH900776 added to NAs enhanced signaling towards Chk1 (pSer317/pSer345), effectively blocked Chk1 activation (Ser296 autophosphorylation), increased replication stress (p53 and γ-H2AX accumulation) and temporarily potentiated apoptosis. In p53-defective MEC-1 cell line representing adverse chronic lymphocytic leukemia (CLL), Chk1 inhibition together with NAs led to enhanced and sustained replication stress and significantly potentiated apoptosis. Altogether, among 17 tested cell lines SCH900776 sensitized four of them to all three NAs. Focusing further on MEC-1 and co-treatment of SCH900776 with fludarabine, we disclosed chromosome pulverization in cells undergoing aberrant mitoses. SCH900776 also increased the effect of fludarabine in a proportion of primary CLL samples treated with pro-proliferative stimuli, including those with TP53 disruption. Finally, we observed a fludarabine potentiation by SCH900776 in a T-cell leukemia 1 (TCL1)-driven mouse model of CLL. Collectively, we have substantiated the significant potential of Chk1 inhibition in B-lymphoid cells.

Richter Syndrome in Chronic Lymphocytic Leukemia

The term Richter syndrome (RS) indicates the transformation of chronic lymphocytic leukemia (CLL) into an aggressive lymphoma. RS is a rare complication with an aggressive clinical course, bearing an unfavorable prognosis. In the majority of cases, CLL transforms into RS as diffuse large B cell lymphoma (DLBCL), and a clonal relation between the two processes can be found. However, clonally unrelated RS can occur and transformations to other histologies beside DLBCL have been described. Recent data have shed some light on genetic characteristics that can influence and drive the transformation from CLL to RS. This molecular information has not been translated yet into significant treatment advances, and currently the therapy regimens for RS continue to rely on intensive chemotherapy combinations followed by stem cell transplant in suitable candidates. Based on the rapid pace of discoveries in the field of hematological malignancies and on the recent revolution in the therapeutic landscape for CLL and B cell lymphomas, new therapeutic options for RS might be available in the upcoming years.

Histologic transformation of chronic lymphocytic leukemia/small lymphocytic lymphoma

Although generally considered a clinically indolent neoplasm, CLL/SLL may undergo transformation to a clinically aggressive lymphoma. The most common form of transformation, to DLBCL, is also known as Richter syndrome. Transformation determines the course of the disease and is associated with unfavorable patient outcome. Precise detection of transformation and identification of predictive biomarkers and specific molecular pathways implicated in the pathobiology of transformation in CLL/SLL will enable personalized therapeutic approach and provide potential avenues for improving the clinical outcome of patients. In this review, we present an overview of the pathologic features, risk factors, and pathogenic mechanisms of CLL/SLL transformation. Am. J. Hematol. 91:1036-1043, 2016. © 2016 Wiley Periodicals, Inc.