Prognostic models for newly-diagnosed chronic lymphocytic leukaemia in adults: a systematic review and meta-analysis

BACKGROUND

Chronic lymphocytic leukaemia (CLL) is the most common cancer of the lymphatic system in Western countries. Several clinical and biological factors for CLL have been identified. However, it remains unclear which of the available prognostic models combining those factors can be used in clinical practice to predict long-term outcome in people newly-diagnosed with CLL.

OBJECTIVES

To identify, describe and appraise all prognostic models developed to predict overall survival (OS), progression-free survival (PFS) or treatment-free survival (TFS) in newly-diagnosed (previously untreated) adults with CLL, and meta-analyse their predictive performances.

SEARCH METHODS

We searched MEDLINE (from January 1950 to June 2019 via Ovid), Embase (from 1974 to June 2019) and registries of ongoing trials (to 5 March 2020) for development and validation studies of prognostic models for untreated adults with CLL. In addition, we screened the reference lists and citation indices of included studies.

SELECTION CRITERIA

We included all prognostic models developed for CLL which predict OS, PFS, or TFS, provided they combined prognostic factors known before treatment initiation, and any studies that tested the performance of these models in individuals other than the ones included in model development (i.e. 'external model validation studies'). We included studies of adults with confirmed B-cell CLL who had not received treatment prior to the start of the study. We did not restrict the search based on study design.

DATA COLLECTION AND ANALYSIS

We developed a data extraction form to collect information based on the Checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies (CHARMS). Independent pairs of review authors screened references, extracted data and assessed risk of bias according to the Prediction model Risk Of Bias ASsessment Tool (PROBAST). For models that were externally validated at least three times, we aimed to perform a quantitative meta-analysis of their predictive performance, notably their calibration (proportion of people predicted to experience the outcome who do so) and discrimination (ability to differentiate between people with and without the event) using a random-effects model. When a model categorised individuals into risk categories, we pooled outcome frequencies per risk group (low, intermediate, high and very high). We did not apply GRADE as guidance is not yet available for reviews of prognostic models.

MAIN RESULTS

From 52 eligible studies, we identified 12 externally validated models: six were developed for OS, one for PFS and five for TFS. In general, reporting of the studies was poor, especially predictive performance measures for calibration and discrimination; but also basic information, such as eligibility criteria and the recruitment period of participants was often missing. We rated almost all studies at high or unclear risk of bias according to PROBAST. Overall, the applicability of the models and their validation studies was low or unclear; the most common reasons were inappropriate handling of missing data and serious reporting deficiencies concerning eligibility criteria, recruitment period, observation time and prediction performance measures. We report the results for three models predicting OS, which had available data from more than three external validation studies: CLL International Prognostic Index (CLL-IPI) This score includes five prognostic factors: age, clinical stage, IgHV mutational status, B2-microglobulin and TP53 status. Calibration: for the low-, intermediate- and high-risk groups, the pooled five-year survival per risk group from validation studies corresponded to the frequencies observed in the model development study. In the very high-risk group, predicted survival from CLL-IPI was lower than observed from external validation studies. Discrimination: the pooled c-statistic of seven external validation studies (3307 participants, 917 events) was 0.72 (95% confidence interval (CI) 0.67 to 0.77). The 95% prediction interval (PI) of this model for the c-statistic, which describes the expected interval for the model's discriminative ability in a new external validation study, ranged from 0.59 to 0.83. Barcelona-Brno score Aimed at simplifying the CLL-IPI, this score includes three prognostic factors: IgHV mutational status, del(17p) and del(11q). Calibration: for the low- and intermediate-risk group, the pooled survival per risk group corresponded to the frequencies observed in the model development study, although the score seems to overestimate survival for the high-risk group. Discrimination: the pooled c-statistic of four external validation studies (1755 participants, 416 events) was 0.64 (95% CI 0.60 to 0.67); 95% PI 0.59 to 0.68. MDACC 2007 index score The authors presented two versions of this model including six prognostic factors to predict OS: age, B2-microglobulin, absolute lymphocyte count, gender, clinical stage and number of nodal groups. Only one validation study was available for the more comprehensive version of the model, a formula with a nomogram, while seven studies (5127 participants, 994 events) validated the simplified version of the model, the index score. Calibration: for the low- and intermediate-risk groups, the pooled survival per risk group corresponded to the frequencies observed in the model development study, although the score seems to overestimate survival for the high-risk group. Discrimination: the pooled c-statistic of the seven external validation studies for the index score was 0.65 (95% CI 0.60 to 0.70); 95% PI 0.51 to 0.77.

AUTHORS' CONCLUSIONS

Despite the large number of published studies of prognostic models for OS, PFS or TFS for newly-diagnosed, untreated adults with CLL, only a minority of these (N = 12) have been externally validated for their respective primary outcome. Three models have undergone sufficient external validation to enable meta-analysis of the model's ability to predict survival outcomes. Lack of reporting prevented us from summarising calibration as recommended. Of the three models, the CLL-IPI shows the best discrimination, despite overestimation. However, performance of the models may change for individuals with CLL who receive improved treatment options, as the models included in this review were tested mostly on retrospective cohorts receiving a traditional treatment regimen. In conclusion, this review shows a clear need to improve the conducting and reporting of both prognostic model development and external validation studies. For prognostic models to be used as tools in clinical practice, the development of the models (and their subsequent validation studies) should adapt to include the latest therapy options to accurately predict performance. Adaptations should be timely.

Canadian evidence-based guideline for the first-line treatment of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (cll) is the most common adult leukemia in North America. In Canada, no unified national guideline exists for the front-line treatment of cll; provincial guidelines vary and are largely based on funding. A group of clinical experts from across Canada developed a national evidence-based treatment guideline to provide health care professionals with clear guidance on the first-line management of cll. Consensus recommendations based on available evidence are presented for the first-line treatment of cll.

Approaches to Chronic Lymphocytic Leukemia Therapy in the Era of New Agents: The Conundrum of Many Options

Three small molecule inhibitors have been approved for the treatment of chronic lymphocytic leukemia (CLL) in the last 4 years. Ibrutinib, idelalisib, and venetoclax are oral agents with excellent efficacy and different toxicity profiles. Issues discussed herein include the current role for chemoimmunotherapy in CLL, the use of oral inhibitors in older patients, and the sequencing of these molecules in daily practice.

Improved survival for patients diagnosed with chronic lymphocytic leukemia in the era of chemo-immunotherapy: a Danish population-based study of 10455 patients

The treatment of chronic lymphocytic leukemia (CLL) is in rapid transition, and during recent decades both combination chemotherapy and immunotherapy have been introduced. To evaluate the effects of this development, we identified all CLL patients registered in the nation-wide Danish Cancer Register between 1978 and 2013. We identified 10 455 CLL patients and 508 995 CLL-free control persons from the general population. Compared with the latter, the relative mortality rate between CLL patients and their controls decreased from 3.4 (95% CI 3.2-3.6) to 1.9 (95% CI 1.7-2.1) for patients diagnosed in 1978-1984 and 2006-2013, respectively. The improved survival corresponded to a decreasing risk of death from malignant hematological diseases, whereas the risk of death from infections was stable during the study period. These population-based data substantiate the improved survival for patients treated with chemo-immunotherapy demonstrated in clinical studies.

Combination of Targeted Drugs to Control Chronic Lymphocytic Leukemia: Harnessing the Power of New Monoclonal Antibodies in Combination With Ibrutinib

The landscape of treatment for chronic lymphocytic leukemia is rapidly changing at present. Considerable improvement has been achieved with the introduction of the anti-CD20 antibodies, and chemoimmunotherapy has now become an established standard for patients without the high-risk features del(17p)/TP53 mutation. Also, the outcome of patients with these adverse genetic aberrations was dramatically improved with the introduction of the kinase inhibitors ibrutinib and idelalisib. Different combinations of these and additional novel agents are currently evaluated in clinical trials. The combination of the Bruton tyrosine kinase inhibitor ibrutinib with an anti-CD20 antibody is an attractive option, because both drugs act synergistically: ibrutinib redistributes the CLL cells from their homing organs to the peripheral blood, and obinutuzumab eliminates the leukemic cells in the blood with particular efficiency. Adding the Bcl-2 antagonist venetoclax could further intensify the treatment of CLL. This combination might hold the potential to achieve a deep remission with an eradication of residual CLL cells and thus lead to long-term remissions of CLL.

Prevention and management of obinutuzumab-associated toxicities: Australian experience

Patients with chronic lymphocytic leukaemia (CLL) are typically diagnosed at an advanced age and may have multiple co-existing conditions, augmenting the challenges of treating their CLL. Aggressive cytotoxic therapies are often poorly tolerated in this patient population. Obinutuzumab is a glycoengineered type II anti-CD20 monoclonal antibody indicated in combination with chlorambucil for previously untreated CLL. The approval of this drug was based on the pivotal CLL11 trial, which demonstrated longer progression-free survival vs. rituximab/chlorambucil and chlorambucil alone in patients with significant co-existing medical conditions and/or poor renal function. However, a higher risk of infusion-related reactions (IRRs) was demonstrated with obinutuzumab-based therapy. We highlight important nursing care considerations to help prevent and successfully manage IRRs and other important adverse events, to improve the treatment experience of patients receiving obinutuzumab infusions and to enable them to complete their treatment and receive optimal benefit. Premedication, drug handling, dosing, administration, monitoring and documentation are discussed.

Complex karyotypes and KRAS and POT1 mutations impact outcome in CLL after chlorambucil-based chemotherapy or chemoimmunotherapy

Genetic instability is a feature of chronic lymphocytic leukemia (CLL) with adverse prognosis. We hypothesized that chromosomal translocations or complex karyotypes and distinct somatic mutations may impact outcome after first-line chemoimmunotherapy of CLL patients. We performed metaphase karyotyping and next-generation sequencing (NGS) of 85 genes in pretreatment blood samples obtained from 161 patients registered for CLL11, a 3-arm phase 3 trial comparing frontline chlorambucil (Clb) vs Clb plus rituximab (Clb-R) or Clb plus obinutuzumab in CLL patients with significant comorbidity. Chromosomal aberrations as assessed by karyotyping were observed in 68.8% of 154 patients, 31.2% carried translocations, and 19.5% showed complex karyotypes. NGS revealed 198 missense/nonsense mutations and 76 small indels in 76.4% of patients. The most frequently mutated genes were NOTCH1, SF3B1, ATM, TP53, BIRC3, POT1, XPO1, and KRAS Sole chemotherapy, treatment with Clb-R, or genetic lesions in TP53 (9.9% of patients) and KRAS (6.2% of patients) were significantly associated with nonresponse to study therapy. In multivariate models, complex karyotypes and POT1 mutations (8.1% of patients) represented significant prognostic factors for an unfavorable survival, independently of IGHV mutation status, Binet stage, and serum β-2-microglobuline. Patients with the copresence of complex karyotypes and deletions/mutations involving TP53 demonstrated a particularly short survival. In summary, this is the first prospective, controlled study in CLL patients that shows a role of complex karyotype aberrations as an independent prognostic factor for survival after front-line therapy. Moreover, the study identifies mutations in KRAS and POT1 as novel determinants of outcome after chemoimmunotherapy using chlorambucil and anti-CD20 treatment.

Advances in first-line treatment of chronic lymphocytic leukemia: current recommendations on management and first-line treatment by the German CLL Study Group (GCLLSG)

The management of patients with CLL is undergoing significant changes; during the last decade, the outcome of first-line therapies has been markedly improved with the addition of anti-CD20 antibodies to chemotherapy. Today, chemoimmunotherapy for physically fit patients ≤ 65 years should consist of fludarabine, cyclophosphamide, and rituximab (FCR). The combination of bendamustine and rituximab (BR) should be considered in physically fit patients > 65 years and in patients with a higher risk of infections. Patients with reduced fitness and/or relevant comorbidity should receive chlorambucil with a CD20 antibody, preferably obinutuzumab. Regardless of their fitness, patients with CLL carrying genetic aberrations such as del(17p) and/or TP53 mutation poorly respond to chemoimmunotherapy and therefore require different therapeutic approaches. An increasing understanding of the disease biology has led to the development of targeted drugs for the treatment of CLL, such as the BTK inhibitor ibrutinib and PI3K inhibitor idelalisib. These agents have shown efficacy in high-risk and relapsed/refractory patients and are currently being evaluated in clinical trials for first-line therapy. It is anticipated that these compounds and further other novel agents will profoundly change the therapy of CLL.

A phase 2 study of idelalisib plus rituximab in treatment-naïve older patients with chronic lymphocytic leukemia

Idelalisib is a first-in-class oral inhibitor of PI3Kδ that has shown substantial activity in patients with relapsed/refractory chronic lymphocytic leukemia (CLL). To evaluate idelalisib as initial therapy, 64 treatment-naïve older patients with CLL or small lymphocytic leukemia (median age, 71 years; range, 65-90) were treated with rituximab 375 mg/m(2) weekly ×8 and idelalisib 150 mg twice daily continuously for 48 weeks. Patients completing 48 weeks without progression could continue to receive idelalisib on an extension study. The median time on treatment was 22.4 months (range, 0.8-45.8+). The overall response rate (ORR) was 97%, including 19% complete responses. The ORR was 100% in patients with del(17p)/TP53 mutations and 97% in those with unmutated IGHV. Progression-free survival was 83% at 36 months. The most frequent (>30%) adverse events (any grade) were diarrhea (including colitis) (64%), rash (58%), pyrexia (42%), nausea (38%), chills (36%), cough (33%), and fatigue (31%). Elevated alanine transaminase/aspartate transaminase was seen in 67% of patients (23% grade ≥3). The combination of idelalisib and rituximab was highly active, resulting in durable disease control in treatment-naïve older patients with CLL. These results support the further development of idelalisib as initial treatment of CLL. This study is registered at ClinicalTrials.gov as #NCT01203930.

Novel and emerging targeted-based cancer therapy agents and methods

After several decades of uncovering the cancer features and following the improvement of therapeutic agents, however cancer remains as one of the major reasons of mortality. Chemotherapy is one of the main treatment options and has significantly improved the overall survival of cancer patients, but chemotherapeutic agents are highly toxic for normal cells. Therefore, there is a great unmet medical need to develop new therapeutic principles and agents. Targeted-based cancer therapy (TBCT) agents and methods have revolutionized the cancer treatment efficacy. Monoclonal antibodies (mAbs) and small molecule inhibitors (SMIs) are among the most effective agents of TBCT. These drugs have improved the prognosis and survival of cancer patients; however, the therapeutic resistance has subdued the effects. Several mechanisms lead to drug resistance such as mutations in the drug targets, activation of compensatory pathways, and intrinsic or acquired resistance of cancer stem cells. Therefore, new modalities, improving current generation of inhibitors and mAbs, and optimizing the combinational therapy regimens are necessary to decrease the current obstacles in front of TBCT. Moreover, the success of new TBCT agents such as mAbs, SMIs, and immunomodulatory agents has sparked further therapeutic modalities with novel targets to inhibit. Due to the lack of cumulative information describing different agents and methods of TBCT, this review focuses on the most important agents and methods of TBCT that are currently under investigation.

Obinutuzumab: a novel anti-CD20 monoclonal antibody for previously untreated chronic lymphocytic leukemia

OBJECTIVE

To review and summarize data on obinutuzumab, which was approved by the Food and Drug Administration (FDA) in November 2013 for use in combination with chlorambucil for previously untreated chronic lymphocytic leukemia (CLL).

DATA SOURCES

A PubMed literature search (August 2002 to March 2014) was conducted using the terms obinutuzumab, GA101, anti-CD20 antibody, and CLL. Data were also obtained through the FDA briefing documents and American Society of Hematology abstracts.

STUDY SELECTION AND DATA EXTRACTION

The literature search was limited to human studies published in English. Priority was placed on trials of obinutuzumab in previously untreated CLL.

DATA SYNTHESIS

Obinutuzumab is a novel glycoengineered type II anti-CD20 monoclonal antibody, with a higher affinity for CD20 epitope, leading to superior cytotoxicity compared with rituximab. The FDA approval was based on a phase III, randomized trial of chlorambucil monotherapy (n = 118), chlorambucil plus obinutuzumab (n = 333), or rituximab (n =330) in previously untreated elderly CLL patients. Obinutuzumab was administered intravenously as 1000 mg on days 1, 8, and 15 of cycle 1 and day 1 for subsequent cycles. Median progression-free survival was 26.7 months in the chlorambucil plus obinutuzumab arm. The incidence of grade 3 or higher adverse events in the obinutuzumab plus chlorambucil arm was as follows: neutropenia (33%), infusion-related reactions (20%), thrombocytopenia (10%), and infections (7%).

CONCLUSION

Obinutuzumab in combination with chlorambucil is a safe and effective new treatment option for previously untreated elderly CLL patients. It should become the new preferred therapy for these patients with significant comorbidities who are not candidates for fludarabine-based therapy.

Development of a comprehensive prognostic index for patients with chronic lymphocytic leukemia

In addition to clinical staging, a number of biomarkers predicting overall survival (OS) have been identified in chronic lymphocytic leukemia (CLL). The multiplicity of markers, limited information on their independent prognostic value, and a lack of understanding of how to interpret discordant markers are major barriers to use in routine clinical practice. We therefore performed an analysis of 23 prognostic markers based on prospectively collected data from 1948 CLL patients participating in phase 3 trials of the German CLL Study Group to develop a comprehensive prognostic index. A multivariable Cox regression model identified 8 independent predictors of OS: sex, age, ECOG status, del(17p), del(11q), IGHV mutation status, serum β2-microglobulin, and serum thymidine kinase. Using a weighted grading system, a prognostic index was derived that separated 4 risk categories with 5-year OS ranging from 18.7% to 95.2% and having a C-statistic of 0.75. The index stratified OS within all analyzed subgroups, including all Rai/Binet stages. The validity of the index was externally confirmed in a series of 676 newly diagnosed CLL patients from Mayo Clinic. Using this multistep process including external validation, we developed a comprehensive prognostic index with high discriminatory power and prognostic significance on the individual patient level. The studies were registered as follows: CLL1 trial (NCT00262782, http://clinicaltrials.gov), CLL4 trial (ISRCTN 75653261, http://www.controlled-trials.com), and CLL8 trial (NCT00281918, http://clinicaltrials.gov).

Treatment of elderly patients with chronic lymphocytic leukemia: an unmet cinical need

In chronic lymphocytic leukemia (CLL), the most prevalent lymphoid malignancy in western countries, patients have a median age at diagnosis of 72 years. In the last few years, there has been remarkable progress in understanding the biology of CLL, the detection of molecular prognostic factors and the development of more effective therapies. However, many of the milestone studies were conducted in populations that were considerably younger than the average age of the CLL population. Today, the challenge is to improve management of elderly patients. In this population, outcome of treatment with newer highly effective therapies is often compromised by comorbidities and poor performance status. Decision on how elderly patients should be treated is thus a complex issue. The management of these patients should rely on the development of risk-stratified treatment strategies based on the assessment of individual functional status and the biologic characteristics of CLL. New single agents with reduced toxic effects (i.e., inhibitors of BCR signalling) that have achieved promising results in Phase I/II studies when available should modify the paradigm of the treatment of elderly patients with CLL.

Treatment of older patients with chronic lymphocytic leukemia: key questions and current answers

Despite the advanced age at onset, chronic lymphocytic leukemia (CLL) shortens the life expectancy of the majority of newly diagnosed patients. The management of elderly patients with CLL is more complex than that of younger patients due to the greater frequency of comorbidities and functional impairment as well as reduced organ function. Many of the recent advances in the care of CLL patients (prognostication, more intense combination therapy regimens) are of unclear relevance for elderly patients. This review addresses 5 key questions in the management of elderly patients with CLL: (1) why is classifying the “fitness” of CLL patients necessary; (2) what criteria should be used to classify patient fitness; (3) when should elderly patients be treated; (4) how should therapy be selected for elderly patients; and (5) which therapy is best (for this patient)?

Synthesis and evaluation of folate-based chlorambucil delivery systems for tumor-targeted chemotherapy

The development of tumor-targeting drug delivery systems, able to selectively transport cytotoxic agents into the tumor site by exploiting subtle morphological and physiological differences between healthy and malignant cells, currently stands as one of the most attractive anticancer strategies used to overcome the selectivity problems of conventional chemotherapy. Owing to frequent overexpression of folate receptors (FRs) on the surface of malignant cells, conjugation of cytotoxic agents to folic acid (FA) via suitable linkers have demonstrated to enhance selective drug delivery to the tumor site. Herein, the chemical synthesis and biological evaluation of two novel folate-conjugates bearing the anticancer agent chlorambucil (CLB) tethered to either an aminoether (4,7,10-trioxa-1,13-tridecanediamine) or a pseudo-β-dipeptide (β-Ala-ED-β-Ala) linker is reported. The two drug delivery systems have been prepared in high overall yields (54% and 34%) through straightforward and versatile synthetic routes. Evaluation of cell specificity was examined using three leukemic cell lines, undifferentiated U937 (not overexpressing FRs, FR(-)), TPA-differentiated U937 (overexpressing FRs, FR(+)), and TK6 (FR(+)) cells. Both conjugates exhibited high specificity only to FR(+) cells (particularly TK6), demonstrating comparable antitumor activity to CLB in its free form. These data confirm the reliability of folate-based drug delivery systems for targeted antitumor therapy; likewise, they lay the foundations for the development of other folate-conjugates with antitumor potential.

Prevention of neutropenia-related events in elderly patients with hematological cancer

The aging of the population makes it necessary to define more precisely the needs of elderly patients in terms of anticancer therapy as the number of older cancer patients is expected to increase. There is evidence that many elderly cancer patients can benefit from relatively aggressive treatments, provided major side effects can be prevented or treated. In patients with hematological malignancies, infection is the most common and threatening complication resulting from chemotherapy administration. Discussion of the prevention of infection in the setting described above is the aim of this paper.

Optimal management of older patients with chronic lymphocytic leukemia: some facts and principles guiding therapeutic choices

Chronic lymphocytic leukemia (CLL) is a disease of older patients and median age at diagnosis is 72 years. This older group is under-represented in clinical trials, (median age 58-62 years). Here we review background data on incidence, survival, definitions of older age, fitness criteria, frailty and co-morbidities. Issues influencing the choice of therapy in older patients are also addressed and different therapeutic options are highlighted based on recent available data. Fit older patients with less co-morbidities benefit most from the very effective chemoimmunotherapy (FC-R) given for younger patients today, but whether other novel drug combinations or new agents are more suitable for less fit patients is still unsettled. Based on careful evaluation of published data from larger clinical trials and major referral centers we present our concept of therapy as a guide to optimal management for subgroups of older patients with CLL.