Baseline BCR-ABL1 transcript type of e13a2 and large spleen size are predictors of poor long-term outcomes in chronic phase chronic myeloid leukemia patients who failed to achieve an early molecular response after 3 months of imatinib therapy

Frequencies of BCR::ABL1 Transcripts in Patients with Chronic Myeloid Leukemia: A Meta-Analysis

Chronic myeloid leukemia (CML) is associated with the Philadelphia chromosome and distinct BCR::ABL1 gene transcripts. We assessed the frequencies of these transcripts in Mexico, Latin America, and worldwide. We determined the prevalence of BCR::ABL1 transcripts in CML patients and intercontinental or regional variations using specialized databases and keywords. We analyzed 34 studies from 20 countries, encompassing 5795 patients. Keyword-based searches in specialized databases guided data collection. ANOVA was employed for transcript distribution analysis. The b3a2 transcript was most prevalent globally, followed by b2a2, with e1a2 being the least frequent. Interestingly, Mexico City exhibited a higher incidence of b2a2, while b3a2 predominated in the remaining country. Overall, no significant intercontinental or regional variations were observed. b3a2 was the most common BCR::ABL1 transcript worldwide, with b2a2 following closely; e1a2 was infrequent. Notably, this trend remained consistent in Mexico. Evaluating transcript frequencies holds clinical relevance for CML management. Understanding the frequency of transcript informs personalized CML treatments.

A Retrospective Cohort Study of Upfront Nilotinib in Chronic Myeloid Leukemia: A Single-Center Experience

Context Nilotinib is a second-generation BCR-ABL1 tyrosine kinase inhibitor used in the treatment of chronic myeloid leukemia (CML).

Aims We aim to evaluate the responses and safety of upfront Nilotinib therapy in Indian CML patients.

Setting and Design We retrospectively reviewed the medical records of CML patients who received Nilotinib as an upfront treatment at our center between January 1, 2011 and October 15, 2019.The follow-up was taken till March 31, 2020.

Results Forty One patients ( n = 36 chronic phase and five accelerated-phase CML) received frontline Nilotinib. Median age was 39 years (21–63) with male-to-female ratio of 1.1: 1. At 3 months, 96.9% patients achieved BCR-ABL of ≤10% at international scale. By the end of 12 months, 71.5% patients achieved major molecular response (BCR-ABL ≤0.1%) and 91.4% patients achieved complete cytogenetic response assessed by BCR-ABL polymerase chain reaction of ≤1%. Common toxicities observed were weight gain, thrombocytopenia, corrected QT prolongation, and elevated serum amylase in 14 (34.1%), 7(17.07%), 4(9.7%), and 4(9.7%) patients, respectively. Overall, five patients had loss of response with further progression and death in three patients. At a median of 43.7 months, 38 patients survived with estimated 3 year event-free survival and overall survival of 65 ± 9 and 93 ± 5%.

Conclusion This study showed remarkable good response with upfront Nilotinib in Indian patients with CML.

The prognostic importance of BCR-ABL transcripts in Chronic Myeloid Leukemia: A systematic review and meta-analysis

BACKGROUND

Chronic Myeloid Leukemia (CML) is characterized by the overproduction of BCR-ABL, a tyrosine kinase with constitutive activity, in which the majority of CML patients have e13a2 or e14a2 transcripts. Reckoned the possible associations between the hematologic and molecular features of the disease, a profound understanding of different aspects of this neoplasm would be provided.

METHOD

The authors implemented a systematic literature search, utilizing the terms published articles or internationally accepted abstracts from PubMed, Embase, Medline, Cochrane library before January 2019. Weighted mean proportion and 95 % confidence intervals (CIs) of CML prevalence calculated using a fixed-effects and a random-effects model. Statistical heterogeneity was evaluated using the I2 statistic.

RESULTS

34 studies for a total of 54,034 Patients were selected and included in the review. Results revealed that compared to e13a2 group, the overall estimated prevalence is much higher in the e14a2 (39 % and 54 %, respectively). Besides, the overall estimated prevalence ratio of male to female was higher in the e13a2 group in comparison to e14a2 (1.08 and 0.856 respectively). The overall estimated prevalence of dual transcription of e13a2/e14a2 was 1.11 %, and male/female overall estimated prevalence ratio was 1.18.

CONCLUSION

This meta-analysis of CML patients demonstrated the e14a2 as the more common transcript type. Usually, the e14a2 transcript is prevalent in females, whereas e13a2 and dual transcription of e13a2/e14a2 are more common in men. These data explicate that the differences in proportion are not by chance. This is crucial, as the transcript type is a variable suspected to be of prognostic importance for the treatment-related response, the outcome of treatment, and the rate of treatment-free remission.

Prognostic Significance of Transcript-Type BCR - ABL1 in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is characterized by the presence of the BCR-ABL1 fusion gene. In more than 95% of CML patients, the typical BCR-ABL1 transcript subtypes are e13a2 (b2a2), e14a2 (b3a2), or the simultaneous expression of both. Other less frequent transcript subtypes, such as e1a2, e2a2, e6a2, e19a2, e1a3, e13a3, and e14a3, have been sporadically reported. The main purpose of this review is to assess the possible impact of different transcripts on the response rate to tyrosine kinase inhibitors (TKIs), the achievement of stable deep molecular responses (s-DMR), the potential maintenance of treatment-free remission (TFR), and long-term outcome of CML patients treated with TKIs. According to the majority of published studies, patients with e13a2 transcript treated with imatinib have lower and slower cytogenetic and molecular responses than those with e14a2 transcript. They should be considered a high-risk group that would most benefit from frontline treatment with second-generation TKIs (2GTIKIs). Although few studies have been published, similar significant differences in response rates to 2GTKIs have been not reported. The e14a2 transcript seems to be a favorable prognostic factor for obtaining s-DMR, irrespective of the TKI received, and is also associated with a very high rate of TFR maintenance. Indeed, patients with e13a2 transcript achieve a lower rate of s-DMR and experience a higher probability of TFR failure. According to most reported data in the literature, the type of transcript does not seem to affect long-term outcomes of CML patients treated with TKIs. In TFR, the e14a2 transcript appears to be related to favorable responses. 2GTKIs as frontline therapy might be a convenient approach in patients with e13a2 transcript to achieve optimal long-term outcomes.

Chronic myeloid leukemia: the concepts of resistance and persistence and the relationship with the BCR-ABL1 transcript type

Chronic myeloid leukemia is driven by a hybrid gene, BCR-ABL1, that codes for a leukemogenic tyrosine kinase (TK) protein of 210 KDa (p210^BCR-ABL1). Resistance to TK inhibitor (TKI) therapy occurs in relatively few patients, no more than 10%, while persistence of minimal residual disease during TKI therapy occurs in the great majority of patients. Resistance is a cause of death, persistence is compatible with a fairly normal length and quality of life, but may require lifelong treatment. The causes of resistance are heterogeneous, including the development of other genomic abnormalities or the altered expression of other genes, requiring different treatments. The causes of persistence may not be the same as those of resistance. We hypothesize that the variability in breakpoint position within the Major-breakpoint cluster region (M-bcr), resulting in two different messenger RNAs that may or may not include exon 14 of BCR (e13a2 and e14a2, respectively), and, as a consequence, in two p210^BCR-ABL1 proteins that differ by 25 amino acids, may be a cause of persistence. The hypothesis is based on a critical review of the relationships between the BCR-ABL1 transcript types, the response to TKIs, the outcome of treatment, and the immune response, suggesting that the e14a2 transcript is associated with more and deeper molecular responses, hence with a higher probability of achieving treatment-free remission (TFR). Investigating this putative cause of persistence may help bringing more patients into stable TFR.

BCR-ABL1 transcript levels at 4 weeks have prognostic significance for time-specific responses and for predicting survival in chronic-phase chronic myeloid leukemia patients treated with various tyrosine kinase inhibitors

The present study aimed to assess the clinical impact of BCR‐ABL1 transcript levels determined at an earlier time point than the 3‐month early molecular response (EMR) in chronic‐phase chronic myeloid leukemia (CML‐CP) patients. BCR‐ABL1 transcript levels of CML‐CP patients (n = 258; median age, 43 [range, 18‐81] years) treated with various tyrosine kinase inhibitors (TKIs) were determined at 4 weeks (28 ± 3 days) and at every 3 months of treatment initiation. At 4 weeks, receiver operating characteristic curves revealed that cutoff values of BCR‐ABL1 transcripts for achieving major molecular responses (MMRs) by 12 and 60 months were 40.89% and 39.16%, respectively (95% CI, 0.658‐0.772 and 95% CI, 0.643‐0.758; P < 0.0001). With 40% of BCR‐ABL1 transcripts at 4 weeks (very early MR; VEMR), patients with VEMR achieved higher 3‐month EMR and 4‐week VEMR significantly associated with higher cumulative incidences of 5‐year MMR (89.1% vs 72.3%; P < 0.001) and 5‐year deep molecular response (DMR) (56.5% vs 29.4%; P = 0.001). Furthermore, event‐free survival (EFS)‐a (93.0% vs 84.8%; P = 0.068) and EFS‐b (71.1% vs 57.9%; P = 0.061) by 5 years were also marginally significant. VEMR and 3‐month EMR were achieved in 89 patients, with significantly superior outcomes. In multivariate analyses, lower leukocyte count (P = 0.008) and frontline second‐generation TKI therapy size (P < 0.001) were significantly associated with VEMR achievement, but not baseline BCR‐ABL1 level and CML duration. In conclusion, the 4‐week BCR‐ABL1 transcript levels including VEMR could be important to predict long‐term outcomes and may provide additional information about innate intrinsic sensitivity to CML among individuals.