Comparative assessment of prognostic models in chronic lymphocytic leukemia: evaluation in Indian cohort

How Do We Manage Chronic Lymphocytic Leukemia in India

PURPOSE OF REVIEW

Chronic lymphocytic leukemia was an ignored leukemia in India until a decade back, given its low prevalence and absence of novel drugs to treat it. Healthcare in India is heterogeneous, with variations in population, health systems, and reimbursement options. We have focused on opinions from three hemato-oncologists incorporating an opinion poll from 44 hemato-oncologists across India on the common issues in CLL to give an idea of the practice pan-India.

RECENT FINDINGS

More CLL patients are being diagnosed in their early stages. There is an attempt to use prognostic and predictive markers in making shared decisions for managing CLL. There is still a role for chemoimmunotherapy (CIT) in India, given limited health insurance coverage. But with the availability of inexpensive generics, the patient preference for non-CIT options like Bruton's tyrosine kinase (BTK) inhibitors is palpable. The CLL scene in India is changing rapidly. With the wide availability of economical generic small molecule inhibitors, monoclonal antibodies, and coverage by social health insurance schemes, India is poised to cater to most CLL patient needs.

Evaluation of the CLL-IPI and IPS-E Prognostic Indices in a Young Middle Eastern Population with Chronic Lymphocytic Leukemia: A Retrospective Analysis at the Kuwait Cancer Control Center

INTRODUCTION

The Chronic Lymphocytic Leukemia International Prognostic Index (CLL-IPI) is a powerful prognostic tool validated in multiple Western populations. However, its utility in the young Middle Eastern population is unknown.

METHODOLOGY

We conducted a retrospective analysis of 152 unselected patients with chronic lymphocytic leukemia (CLL) diagnosed between 2008 and 2022 at the Kuwait Cancer Control Center, which serves as the sole cancer center in Kuwait. The evaluation of the CLL-IPI was based on the assessment of event-free survival (EFS) across the entire cohort. Subsequently, we compared the CLL-IPI with the International Prognostic Score for Early-stage patients (IPS-E) in order to predict the time to first treatment specifically within the subgroup of patients diagnosed with early-stage disease.

RESULTS

The median age of the study cohort was 59.9 years (IQR, 53.1-68.8). The 5-year EFS rates for the low, intermediate, and high/very high-risk categories were approximately 82%, 34%, and 23%, respectively, p < 0.001 (C-statistic = 0.67). On multivariate analysis, advanced stage and unmated IGHV status were independent prognostic factors of EFS. In those with early-stage disease, cumulative 5-year treatment incidence rates for the low, intermediate, and high/very high-risk categories based on the CLL-IPI score were approximately 8%, 55%, and 55%, respectively, p = 0.001 (C-statistic = 0.70). However, based on the IPS-E score, the cumulative 5-year treatment incidence rates for the low, intermediate, and high-risk categories were approximately 0%, 10%, and 60%, respectively, p < 0.001 (C-statistic = 0.73).

CONCLUSIONS

The CLL-IPI and the IPS-E are valid stratification tool in our young Middle Eastern population.

Serum B-Cell Maturation Antigen is an Independent Prognostic Marker in Previously Untreated Chronic Lymphocytic Leukemia

B-cell maturation antigen (BCMA) is a cell membrane receptor expressed on mature B lymphocytes with elevated serum levels found among patients with B-cell malignancies, including chronic lymphocytic leukemia (CLL). Serum BCMA (sBCMA) levels were measured in 331 untreated, newly diagnosed CLL patients using an ELISA with a polyclonal anti-BCMA antibody. Elevated sBCMA was found among patients with CLL compared to age- and sex-matched healthy controls and those with more active CLL based on prognostic factors. The relationships between sBCMA, time to first treatment (TTFT), overall survival (OS) and multiple prognostic factors were compared using Mann Whitney and Kruskal-Wallis tests. The median sBCMA level in the CLL cohort (48.6 ng/mL) was significantly higher (p < 0.001) compared to age- and sex-matched healthy subjects (n = 100; 37.8 ng/mL). sBCMA correlated with TTFT (hazard ratio [HR] 2.9, 95% confidence interval [CI] 2.0-4.2, p < 0.001) and OS (HR 2.5, 95% CI 1.5-4.0, p < 0.001). Multiple models were utilized to test the predictive effects of sBCMA, sex, CLL-IPI and IPS-E on TTFT and OS. The addition of sBCMA to CLL-IPI and IPS-E improved their prognostic ability to predict TTFT and OS. Thus, serum BCMA is a new promising prognostic biomarker for CLL.

Chronic Lymphocytic Leukemia: Real-World Data From India

PURPOSE

Chronic lymphocytic leukemia (CLL) is uncommon in India. There are limited studies on CLL from the Indian subcontinent.

METHODS

This was a prospective study (2011-2017) of consecutively diagnosed patients with CLL at a single center. The diagnosis, prognosis, treatment indication, response criteria, and adverse events were recorded as per International Workshop on Chronic Lymphocytic Leukemia guidelines. Biosimilar rituximab dosing (375 mg/m²) was fixed for all cycles. Time to next treatment (TTNT) was defined as the time from front-line treatment initiation to next treatment or death from any cause. Overall survival (OS) was defined as the time from treatment initiation until death from any cause.

RESULTS

A total of 409 patients with CLL were enrolled over the study period. The median follow-up was 32 months (range, 2-135 months). The median age was 61 years, and 31.8% of patients with CLL were ≤ 55 years of age; 43.3% of patients had a cumulative illness rating scale score ≥ 3. Prognostic fluorescence in situ hybridization data were available in 53.3% of patients. Chlorambucil (94/180; 52.2%) and bendamustine + rituximab (BR; 57/180; 31.6%) were the most common regimens used up front. The overall response rates after front-line therapy were 74.4% and 91.2%, respectively. The TTNT was 33 months and not reached, respectively (P = .001). Grade 3/4 neutropenia and infections were seen in 52.6% and 38.5% of patients receiving BR. The median OS was not reached in both regimens (P = .25).

CONCLUSION

Indian patients with CLL are younger in chronological age but have higher morbidity burden. Treatment outcomes with biosimilar fixed-dose BR are comparable to those reported in the literature. Chlorambucil is still a valid option, given the economic burden of the disease and treatment.

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.