Frontline Tyrosine Kinase Inhibitors Research Articles

Real-world outcomes on platinum-containing chemotherapy for EGFR-mutated advanced nonsquamous NSCLC with prior exposure to EGFR tyrosine kinase inhibitors.

Front-line therapy with an EGFR tyrosine kinase inhibitor (TKI) is the standard of care for treating patients with advanced nonsquamous NSCLC with the common sensitizing EGFR exon 19 deletion and exon 21 L858R point mutations. However, EGFR TKI resistance inevitably develops. The optimal subsequent therapy remains to be identified, although platinum-containing chemotherapy regimens are often administered. Our objectives were to describe baseline characteristics, survival, and subsequent treatment patterns for patients with advanced nonsquamous NSCLC with EGFR exon 19 deletion or L858R mutation who received a platinum-based combination regimen after front-line EGFR TKI therapy. This retrospective study used a nationwide electronic health record-derived deidentified database to select adult patients with advanced nonsquamous NSCLC, evidence of EGFR exon 19 deletion or L858R mutation, and ECOG performance status of 0-2 who initiated platinum-containing chemotherapy, with or without concomitant immunotherapy, from 1-January-2011 to 30-June-2020 following receipt of any EGFR TKI as first-line therapy or, alternatively, a first- or second-generation EGFR TKI (erlotinib, afatinib, gefitinib, dacomitinib) as first-line therapy followed by the third-generation EGFR TKI osimertinib as second-line therapy. Data cut-off was 30-June-2022. The Kaplan-Meier method was used to estimate overall survival (OS) after initiation of pemetrexed-platinum (n=119) or any platinum-based combination regimen (platinum cohort; n=311). The two cohorts included two-thirds women (65%-66%) and 57%-58% nonsmokers; median ages were 66 and 65 years in pemetrexed-platinum and platinum cohorts, respectively. Median OS was 10.3 months (95% CI, 8.1-13.9) from pemetrexed-platinum initiation and 12.4 months (95% CI, 10.2-15.2) from platinum initiation; 12-month survival rates were 48% and 51%, respectively; 260 patients (84%) had died by the end of the study. The suboptimal survival outcomes recorded in this study demonstrate the unmet need to identify more effective subsequent treatment regimens for patients with EGFR-mutated advanced nonsquamous NSCLC after EGFR TKI resistance develops.

Baseline Features, Treatment Choice and Early Frontline TKI Permanent Discontinuation in Younger Patients with Chronic Myeloid Leukemia: A “Campus CML” Study

Introduction Median age at diagnosis in patients with Chronic Myeloid Leukemia (CML) is about 60 years: only few data are available in younger subjects at present. Aim To analyze initial features, choice of frontline Tyrosine-Kinase Inhibitor (TKI) and early adverse events leading to permanent TKI discontinuation in the first 12 months from TKI start in newly diagnosed subjects aged ≤ 40 years in a large and unselected real-life cohort of CML patients. Methods We retrospectively evaluated 1963 patients newly diagnosed from 1/2012 to 12/2019 at 38 Hematology Centers in Italy participating at the “Campus CML” project: according to age at diagnosis, 302 were ≤ 40 years [Younger Patients (YP)], 900 were > 45 < 65 years [Intermediate Aged Patients (IAP)] and 761 were ≥ 65 years [Elderly Patients (EP)]. Results Clinical features, frontline TKI and causes of early TKI discontinuation according to age at diagnosis are reported in the Table 1. As to baseline clinical features, YP had significantly higher WBC count, lower Hb levels and higher rate of spleen enlargement: moreover, as expected, low-risk Sokal score was more common and rate of concomitant diseases/number of concomitant drugs lower in YP. As to frontline TKI, 96 YP (31.1%) received imatinib (IM) and 206 (68.9%) a 2G-TKI [dasatinib (DAS) n=60, 19.9%; nilotinib (NIL) n=144, 47.6%]: choice of 2G-TKI as frontline treatment was significantly more common in YP compared to both IAP and EP (p < 0.001). Causes of permanent frontline TKI discontinuation during the first 12 months of treatment according to age at diagnosis are reported in the Table 1: among YP, 45 (14.9%) discontinued frontline TKI treatment due to hematologic toxicity (5 cases, 1.6%), extra-hematologic toxicity (11 cases, 3.7%), primary resistance (24 cases, 8.0%), secondary resistance (2 cases, 0.6%) or evolution in blastic phase (BP) (3 cases, 1.0%). Cumulative incidence of permanent discontinuation at 12 months was 14.6% (95%CI 10.7 - 18.5) in YP compared to 16.9% (95%CI 14.3 - 19.2) in IAP (p=0.388) and 24.0% (95%CI 20.9 - 27.1) in EP (p < 0.001) (Figure 1): considering only permanent TKI discontinuation due to treatment resistance (primary resistance + secondary resistance + evolution in BP), no difference was observed according to age at diagnosis [9.6% (95%CI 6.3 - 12.9) in YP versus 10.2% (95%CI 8.2 - 12.2) in IAP versus 11.8% (95%CI 9.6 - 14.0) in EP, p=0.589]. Conclusions Our data highlight the following peculiar clinical features at baseline and during the first year of treatment in YP with CML compared with IAP and EP: a delayed diagnosis, outlined by higher WBC count and rate of spleen enlargement; an expected choice of 2G-TKI as frontline treatment in the real-life, even if about one third of them was still treated with IM; a lower incidence of early frontline TKI permanent discontinuation compared to EP but not IAP, mainly due to toxic causes and not related to resistance. Data on early molecular response and further evaluations at 24 and 36 months are warranted to complete present analysis.

Ponatinib Versus Imatinib in Patients with Newly Diagnosed Ph+ ALL: Subgroup Analysis of the Phase 3 Phallcon Study

Background: BCR::ABL1 tyrosine kinase inhibitors (TKIs) in combination with chemotherapy or steroids remain the standard of care in patients with newly diagnosed Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL). Most patients treated with first- or second-generation TKIs eventually experience disease progression due to treatment resistance. Ponatinib is the only currently approved pan-BCR::ABL1 inhibitory TKI that potently inhibits wild-type and single resistance mutation variants of BCR::ABL1, including T315I. Multiple studies have shown promising minimal residual disease (MRD) negativity (neg) rates and survival outcomes with ponatinib in combination with chemotherapy or chemotherapy-free regimens. PhALLCON (NCT03589326) is the first randomized study comparing frontline TKIs in adults with Ph+ ALL. The primary endpoint for PhALLCON was met, with a clinically significantly higher MRD-neg complete remission (CR) rate at end of induction (EOI) with ponatinib vs imatinib (34.4% vs 16.7%; risk difference: 0.18 [95% confidence interval (CI): 0.06‒0.29]; P=0.0021) and a manageable safety profile comparable with imatinib. Here we report subgroup efficacy analyses from PhALLCON. Methods: This global, registrational, phase 3, open-label study randomized newly diagnosed adult patients with Ph+ ALL 2:1 to receive ponatinib (30 mg once daily [QD]) or imatinib (600 mg QD) plus reduced-intensity chemotherapy through EOI (Cycles 1-3), consolidation (Cycles 4-9), and post-consolidation (Cycles 10-20). Following post-consolidation, patients continued to receive single-agent ponatinib or imatinib until disease progression or unacceptable toxicity. The composite primary endpoint was MRD-neg ( BCR:: ABL1 ≤0.01% [MR4])CR for 4 weeks at EOI. Event-free survival (EFS; any-cause death, failure to achieve CR by EOI, relapse from CR) was a key secondary endpoint. A post-hoc analysis of progression-free survival (PFS; EFS-defined events, failure to achieve MRD-neg by the end of treatment, and loss of MRD-neg) was conducted. Subgroup analyses were performed relative to baseline demographic and disease characteristics. Results: Of 245 randomized patients, 232 (ponatinib, n=154; imatinib, n=78) had baseline BCR::ABL1 p190/p210 variants verified by central lab (efficacy-evaluable population); median age was 54 years (37.1% ≥60 years). As of Aug 2022, 78 patients (ponatinib/imatinib: 68 [41.5%]/10 [12.3%]) remained on study treatment; the top 3 reasons for discontinuation were hematopoietic stem cell transplantation (HSCT; 30.5%/37.0%), adverse events (12.2%/12.3%), and lack of efficacy (7.3%/25.9%). Median follow-up in the ponatinib and imatinib arms was 20 months and 18 months, respectively. Benefit for ponatinib was observed across all subgroups analyzed ( Table). All age subgroups had higher rates of MRD-neg CR with ponatinib vs imatinib, with the greatest benefit observed in patients ≥60 years (40.0% ponatinib vs 10.3% imatinib; P=0.0005). MRD-neg CR rate was higher for ponatinib vs imatinib among those with the BCR::ABL1 p190 variant (38.6%/17.0%; P=0.0017); it was higher for the p210 variant as well, but not significantly (22.5% vs 16.0%; P=0.51). Median PFS was longer with ponatinib vs imatinib regardless of age, with the greatest difference observed in the subgroup of patients ≥60 years (22.5 months for ponatinib vs 8.3 months for imatinib; hazard ratio: 0.594 [95% CI: 0.332-1.063]). Conclusions: Ponatinib was superior to imatinib in combination with reduced-intensity chemotherapy in the front-line setting for patients with Ph+ ALL, with a clinically significantly higher MRD-neg CR rate at EOI. Benefit was observed across all subgroups, particularly for patients ≥60 years and for those with the BCR::ABL1 p190 variant.

Prospective Assessment of Co-Morbidities and Framingham Risk Score in Newly Diagnosed Chronic Myeloid Leukemia (CML) Patients and Its Impact on Clinical Outcomes Following Frontline TKI Therapy: Toronto CML Genomic Alliance in Greater Toronto Area & Ontario (TCGA-GTA)

Introduction Front-line (1L) tyrosine kinase inhibitor (TKI) drug selection is a pearl of clinical practice in CML. It requires consideration of multiple aspects including the goal of therapy, potency of the drug as well as comorbidity of the patient (pt). Contemporary CML practice emphasizes the importance of comorbidity for TKI selection. However, such data is scarce particularly the prevalence of comorbidity and its impact on 1L drug selection. We are developing a shared care model with community hematologists in Greater Toronto Area (TCGA-GTA). Newly diagnosed CML pts in the community will be referred to the study core center for prospective enrolment into the CML registry, informed consenting for genetic testing/future research, and evaluation of baseline comorbidity. Pt will return to referring hematologists for management of CML, including 1L TKI treatment as per standard of care, and is scheduled to visit the study center at 6 and 12 months, then annually for 10 years. It gives us a unique opportunity to evaluate the impact of comorbidity on 1L TKI drug selection. Patients and method Adult pts with newly diagnosed CML of any phase within 2 months of diagnosis are eligible for the study unless they are not able to visit study core center. Comorbidities and Framingham risk score (FRS) were assessed at the time of initial evaluation. Mutation profile testing is done by a bar-coded error-corrected sequencing platform for 40 genes developed at the Ontario Institute for Cancer Research. Cumulative incidence of molecular response with 2 log (MR2), 3 log (MR3), 4 log reduction or deeper (MR4), and treatment failure (TF) were calculated using cumulative incidence method considering competing risk. Event-free survival (EFS) was defined as time from start of TKI until TKI stop/switch, TF or death. Failure-free survival (FFS) was defined as time from start of TKI to TF [primary resistance, loss of complete cytogenetic response, new additional cytogenetic abnormalities (ACAs), and progression to accelerated or blasts phase (AP/BP)] or death. Results From November 2020 until June 31, 2023 (data cutoff), a total of 77 pts were enrolled in the study. The median follow-up time was 12 months. The frequency of 1L TKI selection was as follows: IMATINIB (IM) (n=23, 30%), DASATINIB (n=25, 32%), NILOTINIB (n=22, 29%), BOSUTINIB (n=1, 1%), ASCIMINIB (n=6, 8%). Majority of the pts were male (n=51, 66%). Ninety-three percent of pts were in chronic phase at diagnosis, while 4% and 3% were in AP and BP, respectively. Presence of ACAs was detected in 18 pts (23%), 10 of which were high risk, while 6% (n=5) were not evaluable. The baseline clinical and disease characteristics of pts on 1L IM vs other TKIs (2G-TKI) are summarised in Table 1. Of note, pts on IM were significantly older with higher FRS and comorbidities, including coronary artery disease, diabetes mellitus, and hypertension. The OS of all pts at 1 year was 98.5% (95% confidence interval 90%-99.8%). At 1 year, pts with intermediate to high risk FRS had lower FFS (73.2% vs 86.5%, p=0.037) while history of hyperlipidemia was associated with lower EFS (59.3% vs 81.5%, p=0.023) and 6 times more likely to stop or switch therapy due to intolerance or resistance (HR 5.9, p=0.002). Baseline comorbidities did not demonstrate signifincant impact on MR2 and MR3 at 1 year but pts with low FRS were more likely to achieve MR4 within 1 year (22.3% vs 0%, p=0.023). Age did not affect any of the clinical and molecular endpoints. Compared to 2G-TKI, IM had worse EFS (HR 3.93, p=0.003), FFS (HR 5.66, p=0.011), and MR2 (47.3% vs 84.4%, p=0.003) at 1 year. Further, IM pts experienced higher rate of any side effects compared to those on 2G-TKI (69.6% vs 31.5%, p=0.003). Conclusion The TCGA-GTA study provides valuable insights into the impact of comorbidity on selection of 1L TKI and its outcome in a real-world setting. Pts who are older and with higher FRS and comorbidities tend to receive 1L IM. However, pts on 1L 2G TKIs are more likely to reach treatment goals faster with lower probability of TF. The present study did not reach a clear conclusion whether the worse outcomes in the pts receiving IM are from IM treatment or concurrent risk factors such as age and comorbidities, thus further study with an expanded cohort and longer follow-up is required. Elderly pts or those with comorbidities would need alternative treatment with better efficacy and tolerability, such as Asciminib, that can overcome comorbidity issues in the future.

Age-Related Clonal Hematopoiesis Mutations Detected at the Time of Stopping Tyrosine Kinase Inhibitor Therapy Predict the Achievement of Treatment-Free Remission for Patients with CML

Background The gain of mutations with a competitive advantage in hematopoietic cells of healthy individuals is common with aging and termed clonal hematopoiesis of indeterminate potential (CHIP). Through sequencing studies we detected CHIP related mutants in chronic myeloid leukemia (CML) patients in deep molecular response. CHIP mutants may provide a selective growth advantage to non-leukemic cells, driving their clonal expansion in remission and potentially influencing treatment-free remission (TFR) if CHIP clones outcompete an emerging BCR:: ABL1 clone. Aim To determine if CHIP mutants detected at the time of stopping tyrosine kinase inhibitor (TKI) therapy could influence achievement of TFR. Methods An RNA-based sequencing method targeting 17 of the most frequently mutated CHIP genes was developed and applied to blood samples of 150 patients who attempted TFR. The median follow up of patients in TFR was 71 months. CHIP mutants met strict criteria for pathogenicity based on their potential to confer growth and survival advantages, i.e. the same criteria as cancer driver mutations. Variant allele frequency (VAF) of ≥0.4% was reproducibly detected. CHIP at the time of cessation, termed CHIP TOC, was defined as 1) ≥1 CHIP mutant with VAF ≥2.0% (n=30 patients) or 2) a novel criterion for patients with multiple CHIP mutants where the combined VAF was ≥2.0% (n=7). Overall, 25/37 patients (68%) with CHIP TOC had multiple mutations, range 2-7. Results CHIP TOC was detected in 37/150 patients (25%). The average age of patients with CHIP TOC was 66.3 years vs 58.0 for those without, P=.0004, which is consistent with the age related nature of CHIP. No patient aged <40 had CHIP TOC, whereas 44% of patients ≥70 had CHIP TOC. Twelve genes were mutated and the most frequent were TET2, DNMT3A, ASXL1 and PPM1D. The overall probability of TFR was 60.4% at 12 months and 53.0% at 84 months. CHIP TOC was associated with TFR. At 12 months, 83.6% of patients with CHIP TOC maintained TFR versus 52.9% of patients without CHIP TOC, P=.002. At 84 months, 62.9% of patients with CHIP TOC maintained TFR versus 49.6% of patients without CHIP TOC, P=.014. We previously demonstrated that e13a2 transcripts and a slow initial decline of BCR:: ABL1 after starting frontline TKI therapy, measured as the number of days over which BCR:: ABL1 halved, were our strongest predictors of relapse. Prognostic factors for the achievement of TFR at 12 and 84 months were examined in multivariable analysis. Candidate prognostic factors were CHIP TOC, BCR:: ABL1 halving time, BCR:: ABL1 transcript type, age at diagnosis, gender, duration of MR4.5 and time on TKI before TKI stop. The independent predictors of TFR at 12 and 84 months were the presence of CHIP TOC at TKI stop, a shorter BCR:: ABL1 halving time (indicating a more rapid initial BCR:: ABL1 decline) and the e14a2 (plus e14a2/e13a2) BCR:: ABL1 transcript type (Table 1). The rate of late relapse, defined as loss of MMR >12 months after cessation, was higher in patients with CHIP TOC. Overall, 85 patients had TFR at 12 months and late relapse occurred in 8. A landmark analysis demonstrated that the probability of maintaining TFR at 84 months for these 85 patients was 93.8% for those without CHIP TOC (n=57) and 75.2% for those with CHIP TOC (n=28), P=.007. The only variable associated with late relapse among the patients with CHIP TOC was fluctuation of BCR:: ABL1 within the first 12 months after cessation, defined as irregular rise and fall comprising 2 consecutive BCR:: ABL1 ratios with loss of MR4.5, or a single loss of MR4. Overall, 13 patients had fluctuation within the first 12 months and 5 of these had late relapse. All 5 had CHIP TOC. Patients with CHIP TOC and stable MR4.5 by 12 months had a 93.8% probability of TFR at 84 months (Table 2). Conclusion The presence of CHIP TOC at TKI cessation, a shorter BCR:: ABL1 halving time and e14a2 BCR:: ABL1 transcripts were independent predictors of TFR at 12 and 84 months. Delayed loss of MMR that occurred for a minority of patients with CHIP TOC may be associated with competition between CHIP clones and a residual leukemic clone. These patients had fluctuating BCR:: ABL1 over the first 12 months after cessation and prior to late relapse. Novel strategies may be warranted to reduce the risk of late relapse for these patients. Patients who sustained TFR by 12 months in stable MR4.5 had a reassuringly low risk of late relapse. CHIP status could be a key variable to guide TFR decision-making and monitoring.

Adverse outcomes for chronic myeloid leukemia patients with splenomegaly and low in vivo kinase inhibition on imatinib

Variability in the molecular response to frontline tyrosine kinase inhibitor (TKI) therapy in chronic myeloid leukemia may be partially driven by differences in the level of kinase inhibition induced. We measured in vivo BCR::ABL1 kinase inhibition (IVKI) in circulating mononuclear cells after 7 days of therapy. In 173 patients on imatinib 600 mg/day, 23% had low IVKI (<11% reduction in kinase activity from baseline); this was associated with higher rates of early molecular response (EMR) failure; lower rates of major molecular response (MMR), and MR4.5 by 36 months, compared to high IVKI patients. Low IVKI was more common (39%) in patients with large spleens (≥10 cm by palpation). Notably 55% of patients with large spleens and low IVKI experienced EMR failure whereas the EMR failure rate in patients with large spleens and high IVKI was only 12% (p = 0.014). Furthermore, patients with large spleen and low IVKI had a higher incidence of blast crisis, inferior MMR, MR4.5, and event-free survival compared to patients with large spleen and high IVKI and remaining patients. In nilotinib-treated patients (n = 73), only 4% had low IVKI. The combination of low IVKI and large spleen is associated with markedly inferior outcomes and interventions in this setting warrant further studies.

Front-Line Tyrosine Kinase Inhibitors in Pediatric Chronic Myeloid Leukemia: A Study on Efficacy and Safety.

We conducted a retrospective study on 51 pediatric patients with newly diagnosed chronic myeloid leukemia chronic phase or accelerated phase. The patients were classified into the IMA group (N = 33), treated with imatinib, and the DSA group (N = 18), treated with dasatinib, as front-line tyrosine kinase inhibitors (TKIs). At 12 months, the rates of complete cytogenetic response were similar between the IMA group (92.3%) and DSA group (100%) (p = 0.305). However, the rate of early molecular response was higher in the DSA group than in the IMA group (100.0% vs. 80.0%, p = 0.043). By 12 and 24 months, the DSA group showed faster and higher cumulative rates of both major (DSA group: 72.2% and 100%, respectively; IMA group: 41.2% and 68.7%, respectively; p = 0.002) and deep molecular responses (DSA group: 26.0% and 43.6%, respectively; IMA group: 13.8% and 17.5%, respectively; p = 0.004). Both TKIs were well tolerated. Although the height standard deviation scores decreased in both groups, the height decline was greater in the DSA group between one and two years from the start of TKI therapy. In this study, dasatinib achieved faster and higher molecular responses with an acceptable safety profile. Further follow-up is necessary to assess the long-term outcomes of TKI treatment in children.

Treatment after failure of frontline therapy of chronic myeloid leukemia in chronic phase including allogeneic hematopoietic stem cell transplantation.

The treatment outcomes of chronic myeloid leukemia in chronic phase (CML-CP) have dramatically improved with comparable life-expectancy to average of general population in tyrosine kinase inhibitor (TKI) era. However, less than a half of patients who started with TKI can remain on frontline TKI. The reasons of switching TKI can be either intolerance or the lack of efficacy. Although a kinase domain (KD) mutation can guide to select salvage TKI from the point of view on the efficacy of TKIs, many factors need to be considered before choosing next-line TKI such as the high-risk features of CML, the adverse events with prior TKI, and the comorbidities of patients. The therapeutic options for CML-CP after failing frontline TKI due to treatment failure or suboptimal responses will be reviewed including allogeneic hematopoietic stem cell transplantation.

DNA Damage Response (DDR) Is Associated With Treatment-free Remission in Chronic Myeloid Leukemia Patients.

DNA Damage Response (DDR) Is Associated With Treatment-free Remission in Chronic Myeloid Leukemia Patients.

Effect of EGFR and ERBB2 amplifications and activating alterations on efficacy of lenvatinib in hepatocellular carcinoma.

600 Background: Hepatocellular carcinoma (HCC) is the most common primary liver cancer and is associated with a high mortality burden. Lenvatinib is an effective frontline tyrosine kinase inhibitor for HCC but is associated with primary and acquired resistance in most patients. Molecular mechanisms of resistance to lenvatinib remain unclear. Methods: We retrospectively analyzed 227 patients with HCC who underwent baseline ctDNA profiling as a component of routine clinical care, including 46 patients who had serial ctDNA analysis done at baseline and after progression to lenvatinib or ICI. Clinical data including demographics, treatment history, tumor responses, and survival outcomes were abstracted from the electronic medical record. Tumor response was categorized according to RECIST 1.1. A national registry of HCC that underwent ctDNA testing using Guardant360 was analyzed to determine the prevalence of EGFR/ERBB2 alterations in HCC. Results: Nearly a third of patients who progressed on lenvatinib demonstrated a gain in EGFR/ ERBB2 amplifications or activating mutations. No consistent trend in EGFR/ ERBB2 amplifications and alterations was found among ICI refractory HCC. Disease control rates (including complete response, partial response, and stable disease) were 20% in EGFR/ERBB2 altered HCC treated with lenvatinib, 62.5% in EGFR/ERBB2 wildtype HCC treated with lenvatinib (p = 0.05), and 58% in EGFR/ERBB2 altered HCC treated with ICIs (p = 0.09). PFS was also longer in EGFR/ERBB2 wildtype HCC treated with lenvatinib (5.9 months) and EGFR/ERBB2 altered HCC treated with ICIs (7.1 months) compared to EGFR/ERBB2 altered HCC treated with lenvatinib (2.2 months, p = 0.002). In a national cohort of 1739 patients with HCC, EGFR amplifications and activating mutations occurred in 6.5% and 1.5% of cases, respectively, and ERBB2 amplifications and activating mutations occurred in 1.9% and 0.7% of cases, respectively. Among EGFR/ERBB2 mutations, we identified recurrent gatekeeper mutations, including multiple A547T and T790M mutations, in 31% of patients. Conclusions: Our study substantiates EGFR/ERBB2 amplifications and mutations as putative drivers of lenvatinib resistance in patients with HCC and identifies the genetic mechanisms for EGFR pathway activation in refractory cancers. EGFR/ERBB2 alterations may thus represent predictive and pharmacodynamic markers of lenvatinib resistance. These findings lend support to the use of EGFR inhibitors combined with lenvatinib in previously untreated or lenvatinib refractory cancers.

Six first-line tyrosine kinase inhibitors reveal novel inhibition potential for the EGFR S768I mutation

Lung cancer, the leading cause of cancer-related mortality, is the most commonly diagnosed cancer. Tyrosine kinase inhibitors (TKIs) are considered a drug-targeted therapy for non-small cell lung cancers (NSCLCs) with epidermal growth factor receptor (EGFR) mutations. However, limited data are available involving the activity of EGFR TKIs against rare EGFR mutations. Here, based on an endogenous EGFR-depleted cell Line H3255 by CRISPR, H3255 cells with rare mutant EGFRS768I and compound mutations EGFRS768I+L858R were tested using cell proliferation assay, cytotoxicity, membrane potential, flow cytometry and Western blot analysis. We conducted cytotoxicity screening of EGFR mutations on six front-line TKIs based on first-, second-, and third-generation TKIs (afatinib, dacomitinib, osimertinib, erlotinib, gefitinib, and icotinib). The results showed that the sensitivity of these mutants containing rare variants EGFRS768I to six front-line TKIs was enriched in the irreversible TKI cytotoxicity assays by determining their change in cytotoxicity, apoptosis, cell proliferation and signal pathway factors. Importantly, the variants harboring EGFRL858R (H3255), EGFRS768I (H3255S768I) and EGFRS768I+L858R (H3255S768I+L858R) were sensitive to six TKIs and induced cytotoxicity through different pathways. Moreover, the compound mutations EGFRS768I+L858R showed more TKI resistance than EGFRS768I mutation and EGFRL858R mutation. We present a comprehensive reference for the sensitivity of EGFRS768I variants to six front-line TKIs. For patients with the EGFR S768I mutation and compound mutations EGFRS768I+L858R, six first-line TKIs appear to be reasonable therapeutic options.

Considerations for the Utility of Real-World Evidence Beyond Trial Data in Advanced NSCLC: The Case of Frontline Tyrosine Kinase Inhibitors.

To extend the discussion on the use of real-world evidence (RWE) in conveying the clinical value of treatment beyond trial data, the primary objective of this study was to assess if efficacy gains in progression-free survival (PFS) observed in randomized controlled trials (RCT) correlate with efficacy gains in the real-world setting. For this, we assessed the treatment benefit of three tyrosine kinase inhibitors (TKIs) in aNSCLC. Using matched cohorts identified in the Flatiron Health database (2011-2020), we mimicked the following cohorts of TKI versus platinum-based chemotherapy (PBC) from the following trials: (1) erlotinib, EURTAC; (2) afatinib, LUX-Lung 3; and (3) crizotinib, PROFILE 1014. Time to treatment discontinuation (TTD) hazard ratio (HR) was used as a proxy for PFS HR, the primary endpoint in the selected RCTs. HRs were calculated via Cox proportional hazard models. Overall, 1,118 patients were included across the three RWE cohorts. Frontline TKI regimens had statistically significantly better real-world TTD than their matched PBC comparator group (HR 0.37, 95% confidence interval [CI] 0.30-0.44 for erlotinib; HR 0.42, 95% CI 0.32-0.55 for afatinib; HR 0.37, 95% CI 0.26-0.53 for crizotinib). The benefit in real-world OS was not different between TKIs and PBC patients, attributed to a high proportion of switching to subsequent therapy. Study findings of relative treatment benefit (HR) for real-world TTD and OS were deemed similar to those for PFS and OS from the pivotal RCTs. The relative treatment effect, measured as real-world TTD HR over the long term, was similar to trial-based PFS HR, implying that the clinical benefit of aNSCLC treatments conveyed in trials translated into the clinical setting. This is important, given that OS data interpretation is limited, even with longer follow-up. Additionally, our RWE analysis endorses TTD as a relevant endpoint to measure clinical benefit.

Permanent Discontinuation of Tyrosine Kinase Inhibitor Frontline Therapy in Patients with Chronic Phase Chronic Myeloid Leukemia Patients during the First 36 Months of Treatment: A "Campus CML" Study

Background Tyrosine kinase inhibitors (TKIs) have changed prognosis and treatment results of chronic myeloid leukemia (CML). However, the first years of therapy are crucial to achieve optimal response, defined as the achievement of deep molecular response: in this early phase, however, different toxicities or suboptimal response/resistance may occur, leading to permanent frontline TKI discontinuation and need for a second-line switch. Methods To evaluate in a large real-life cohort of CML patients the incidence and the different pattern of events leading to a permanent frontline TKI discontinuation during the first 3 years of therapy, 1168 CP-CML patients diagnosed from 1/2012 and 12/2019 at 21 Hematology Centres and treated with frontline imatinib (IM) or second-generation (2G) TKIs dasatinib or nilotinib were retrospectively analysed. Results Frontline TKI was IM in 737 (63.1%) and 2G-TKIs in 431 (36.9%) cases: the main clinical features at diagnosis of the entire cohort and according to frontline treatment are reported in the Table 1. Commonest comorbidities were arterial hypertension (37.4%), previous neoplasm (14.1%), diabetes (10.9%), peripheral vascular diseases (8.4%), ischemic heart disease (6.9%) and COPD (6.7%). IM-treated patients were older (p<0.001) and had more comorbidities (p=0.002 for COPD and p<0.001 for all other diseases). Total number of patients who had discontinued frontline TKI at the 36th month of observation was 391/1168 (33.5%), being higher with IM (294/737, 39.8%) than with 2G-TKIs (96/431, 22.3%) (p<0.001). Cumulative incidence of permanent TKI discontinuation was 19.6% [95% confidence interval (CI) 17.3-21.9] at 12 months, 29.7% (95%CI 27.0-32.4) at 24 months and 34.2% (95%CI 31.5-36.9) at 36 months, respectively: cumulative incidence of discontinuation according to frontline TKI is shown in the Figure (p<0.001 at any time-point). Among the 391 patients who discontinued frontline TKI, the main causes were hematologic toxicity in 27 (6.9%), extra-hematologic toxicity in 106 (27.1%), primary resistance in 166 (42.4%), secondary resistance in 18 (4.6%), evolution in blastic phase in 17 (4.3%), unrelated deaths in 36 (9.2%) and other causes in 21 (5.4%). At univariate analysis, in addition to IM as frontline TKI, baseline factors predictive for an higher rate of TKI discontinuation were age > 65 years (p=0.001), WBC ≥ 100 x 109/l (p<0.001), Hb < 10 g/dl (p<0.001), spleen enlargement ≥ 5 cm below costal margin (p<0.001) and high Sokal score (p<0.001). At multivariate regression logistic analysis, frontline IM (HR 3.22; 95%CI 2.34 - 4.42, p<0.001), WBC ≥ 100 x 109/l (HR 2.18; 95%CI 1.57 - 3.02, p<0.001), spleen enlargement ≥ 5 cm (HR 1.91; 95%CI 1.22 - 3.00, p=0.005) and Sokal high risk (HR 1.78; 95%CI 1.16 - 2.72, p=0.007) retained an independent predictive role on TKI discontinuation. Conclusions This real-world study on over 1100 CML patients reveals that about one third of newly diagnosed CML patients discontinued frontline TKI during the first 3 years of therapy, mostly for primary resistance or toxicity. Discontinuation rates were higher with IM compared to 2G-TKIs at any time-point: however, the impact of older age, higher risks and heavier burden of comorbidities in IM patients should be considered. Other factors seemed to affect the risk of frontline TKI discontinuation but their role needs further refined investigations. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Choice of Tyrosine Kinase Inhibitor and Early Events during the First Year of Therapy in Newly Diagnosed Chronic Phase Chronic Myeloid Leukemia (CML) Patients with Concomitant Diabetes: A "Campus CML" Study

Background Tyrosine kinase inhibitors (TKIs) have dramatically changed the treatment of chronic myeloid leukemia (CML). Most of data on the TKIs safety derive from sponsored controlled trials, where patients with multiple comorbidities had fewer opportunities to be included. Many questions about the management of newly diagnosed CML can only be answered by analysing large cohorts in real world practice. Methods To evaluate the choice of TKI and the incidence of early events during the 1st year of therapy in newly diagnosed chronic phase CML patients with concomitant diabetes, we retrospectively studied 1732 CP-CML patients diagnosed from 1/2012 to 12/2019 at 33 Italian Hematology Centres and treated with frontline imatinib (IM) or second-generation TKIs (2G). Among these, 197 patients (11.4%) had concomitant diabetes. Results The main clinical features at diagnosis of the entire cohort and in patients with diabetes are reported in the Table. Compared with non-diabetic patients, subjects with diabetes were older, had higher Sokal and ELTS scores (Sokal intermediate + high 74.5% vs 59.2%, ELTS intermediate + high 62.6% vs 41.1%) and were more likely affected by other comorbidities as arterial hypertension, COPD, ischemic heart disease/cerebrovascular events and previous neoplasms: as a consequence, diabetic patients reported a higher number of concomitant drugs (> 5 in 38.6% vs 10.1%, p<0.001). The number of white blood cells at diagnosis was lower in diabetic patients (44.9x109/l vs 59.3 x109/l, p=0.008)). Significant differences were observed in the choice of frontline TKI: comparing diabetic with non-diabetic patients, IM was prescribed in 72% vs 54%, dasatinib in 23.4% vs 15.3% and nilotinib in 4.6% vs 30.7% of cases (p<0.001). There were 51 early events (25.9%) in the 1st year of treatment leading to permanent frontline TKI discontinuation in the diabetic patients, compared to 285 (18.7%) in non-diabetic patients (p=0.037). One-year cumulative incidence of TKI permanent discontinuation was 25.9% (95%CI 19.8 - 32.0) in diabetic patients compared to 18.5% (95%CI 16.6 - 20.4) in non-diabetic patients (p=0.015). Conclusions This real-world study on over 1700 CML patients shows that concomitant diabetes is an important factor in newly diagnosed CML patients, affecting both the clinical presentation and the frontline treatment choice: in addition, concomitant diabetes is linked to a high incidence of early events and frontline TKI permanent discontinuation. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

More Than Ten Years Follow-up of Frontline Tyrosine Kinase Inhibitor Therapy in Patients with Chronic Myeloid Leukemia

Background: Tyrosine kinase inhibitor (TKI) therapy improved survival in patients (pts) with chronic myeloid leukemia (CML). Treatment-free remission (TFR) can be considered for a minority of pts, particularly in those who achieved sustained deep molecular response (DMR). Given most pts needs TKI therapy over decades, the aim of this study is to evaluate the very long-term outcome of pts (pts) treated with frontline TKI. Methods: We analyzed 557 pts with newly diagnosed CML in chronic phase (CP) and accelerated phase (AP; based solely on the presence of clonal evolution) who were treated with frontline TKI therapy (standard-dose imatinib, 73 pts; higher-dose imatinib, 210 pts; dasatinib, 144 pts; and nilotinib, 130 pts) from July 2000 to September 2014. The presence of comorbidity was assessed by the Adult Comorbidity Evaluation-27. Responses criteria were previously defined (complete cytogenetic response, CCyR; major molecular response, MMR; molecular response with a 4-log reduction, MR4; molecular response with a 4.5-log reduction, MR4.5). Failure-free survival (FFS) was calculated from the start of therapy to the treatment discontinuation for any reason except of TFR; event-free survival (EFS), to the date of any of the events while on study as defined in the IRIS study; transformation-free survival (TFS), to the date of transformation to accelerated or blast phases during study; overall survival (OS), to the date of death from any cause at any time or date of last follow-up. We evaluated prognostic factors with univariate and multivariate Cox proportional hazard models with a p-value cutoff of 0.100 or less by univariate analysis for variable selections; cumulative incidence of response was assessed with a competing risk model. Multiple imputation was performed for missing variables to reduce bias. Time to complete cytogenetic response was analyzed as a time-dependent variable in the Cox regression Results: The median age at the start of TKI therapy was 49 years (range, 15.1-86.4). The overall median follow-up was 178 months (range, 5.3-253.9) (standard-dose imatinib, 231 months; higher-dose imatinib, 212 months; dasatinib 137 months; nilotinib 138 months) (Table 1). Overall, the 10-year cumulative incidence rates of CCyR, MMR, MR4, and MR4.5 were 91%, 87%, 76%, and 72%, respectively; among pts who responded, the median time to CCyR, MMR, MR4, and MR4.5 were 3.1 months, 5.9 months, 9.5 months, and 12.5 months, respectively. The cumulative incidence rates of CCyR, MMR, MR4, and MR4.5 were higher in the higher-dose imatinib, dasatinib, and nilotinib cohorts compared to standard-dose imatinib. The 10-year FFS rates were 48%, 52%, 67%, and 44% in the standard-dose imatinib, higher-dose imatinib, dasatinib, and nilotinib cohorts, respectively (P<0.001); the 10-year TFS rates were 84%, 98%, 98%, and 96%, respectively (P<0.001); the 10-year EFS rates were 67%, 80%, 89%, 86%, respectively (P=0.001); the 10-year OS rates were 67%, 80%, 89%, and 86%, respectively (P=0.206) (Figure 1). Backward multivariate Cox regression analysis identified older age at TKI therapy, the presence of smoking history, higher severity of comorbidity by the Adult Comorbidity Evaluation-27, higher percentage of blasts in peripheral blood, and longer time to achieve CCyR as adverse prognostic factors for survival. With the minimum median follow-up of more than 10 years in all the TKI groups, the 10-year relative survival rate was 91.4%; among pts who achieved CCyR within 1 year of frontline TKI therapy, the 10-year relative survival rate was 94.4%; MMR, 97.0%; MR4, 96.7%; MR4.5, 96.2%. Conclusion: TKI therapy has significantly improved outcomes of pts with CML-CP. Frontline second-generation TKIs achieve higher rates of DMR response than standard-dose imatinib. The assessment of comorbidity is essential assessment for the optimal selection of frontline TKI therapy. The survival of pts with CML-CP is similar to that of general population at 10 years. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Outcome of Third-Line Tyrosine Kinase Inhibitors in Patients with Chronic Myeloid Leukemia in Chronic Phase: A Propensity Score Analysis

Background: Tyrosine Kinase Inhibitors (TKI) dramatically improve survival in patients with chronic myeloid leukemia in chronic phase (CML-CP). However, patients may develop intolerance of or resistance to TKI therapy over years. Given multiple effective therapies available, the optimal selection of third-line therapy is not clear. The aim of this study is to evaluate the outcomes of third-line TKI therapy in patients with CML-CP. Methods: We retrospectively combined patient-level data of third-line TKI therapy in the clinical trials of PACE and OPTIC studies with patients who received third-line TKI therapy at our institution. Given equivalent outcomes between second-generation TKIs (2G-TKI), we compared the outcomes of patients between 2G-TKI and ponatinib as third-line TKI therapy. Patients with T315I mutations were excluded in our study given the known resistance to all the 2G-TKI therapies. Multiple imputations was performed for missing covariates to reduce bias. Univariate and multivariate Cox regression analysis was performed for survival to identify prognostic factors with a p-value cutoff of 0.05 from univariate to multivariate analysis. One-to-one propensity score matching was performed with a caliper of 0.200, using matching covariates with age at the time of third-line therapy, gender, race, comorbidity, prior TKI therapy, the duration of prior TKI therapy, best prior response during the front-line and second-line TKI therapy, body mass index, white blood cell count, platelet count, percentages of basophils and blasts in peripheral blood, and BCR::ABL1 levels on the international scale. Progression-free survival (PFS) was defined from the start of third-line TKI therapy to the time of loss of major cytogenetic response during the study, progression to accelerated phase or blast phase at any time, death from any cause at any time, or the date of last follow-up; overall survival (OS) was defined as the start of third-line TKI therapy to death from any cause or the date of last follow-up. The Kaplan-Meier method was used for survival with the log-rank test and a significance p-value level of 0.05. Results: We identified 354 patients who received third-line TKI therapy [204 patients (58%) from our institution; 63 patients (18%) from the PACE study; 87 (25%) patients from the OPTIC study] with a median follow-up of 46 months (Table 1). Among them as third-line TKI therapy, 173 patients received 2G-TKI [69 patients (19%), dasatinib; 64 patients (18%), nilotinib; 40 patients (11%), bosutinib], and 181 patients received ponatinib (51%). Overall, the median age at the time of third-line TKI therapy was 54 years (range, 18-87). Prior to third-line TKI therapy, 313 patients (88%) received imatinib; 156 patients (44%), dasatinib; 161 patients (45%), nilotinib; 35 patients (10%), bosutinib. The overall median BCR::ABL1 level was 16.3% on the international scale at the time of third-line TKI therapy. Patients who received ponatinib had higher rates of non-ischemic cardiovascular comorbidity, shorter total duration of prior TKI therapies, higher percentage of basophiles in peripheral blood, and higher levels of BCR::ABL1 on the international scale. Propensity score matching minimized the baseline covariates and identified 96 patients at each group with a median follow-up of 46 months after propensity score matching. There is a tendency of deeper response with ponatinib at baseline BCR::ABL1 levels of >1-10% and >0.1-1% before and after propensity score matching. Using pre-matched data, multivariate Cox regression showed older age at the time of third-line TKI therapy and higher BCR::ABL1 levels as adverse prognostic factors for survival ; the third-line ponatinib therapy was associated with favorable survival [P=0.003; hazard ratio (HR), 0.435; 95% confidence internal (CI), 0.253-0.748]. The 4-year PFS rates were 58% and 75% in the 2G-TKI and ponatinib group, respectively, before matching (P<0.001); the 4-year PFS rates were 78% and 89%, respectively, after matching (P=0.0099). The 4-year OS rates were 57% and 80% in the 2G-TKI and ponatinib group, respectively, before matching; the 4-year OS rates were 78% and 87%, respectively, after matching (Figure 1). Conclusion: Third-line ponatinib therapy is optimal selection for patients with CML-CP who failed prior 2 TKI therapies in the absence of T315I mutation. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Prognostic Model of Transformation to Blast Phase in Patients with Chronic Myeloid Leukemia

Background: Since the advent of Tyrosine kinase inhibitor (TKI) therapy, the survival of patients with chronic myeloid leukemia (CML) is approaching to that of general population. The European LeukemiaNet recommends monitoring reverse transcriptase quantitative PCR for the guidance of molecular response. However, the rare incidence of progression to blast phase may occur during frontline TKI therapy. The aim of this study is to identify prognostic factors for the progression to blast phase during frontline TKI therapy and to develop a nomogram to calculate the risk of transformation at 1 year. Methods: We analyzed 347 patients with newly diagnosed CML in chronic phase (CP) and accelerated phase (AP) who were treated with frontline TKI therapy (standard-dose imatinib, 73 patients; dasatinib, 144 patients; and nilotinib, 130 patients) from July 2000 to September 2014. The presence of comorbidity was assessed by the Adult Comorbidity Evaluation-27. Given the rare incidence of transformation to blast phase and equivalent efficacy of second-generation TKIs between dasatinib and nilotinib, we compared the cumulative incidence of transformation to blast phase between imatinib 400 mg/day and second-generation TKI therapy. We performed univariate and multivariate competing risk regression to identify prognostic factors for cumulative incidence of transformation to blast phase with treatment failure (intolerance, resistance, and/or others) during frontline TKI therapy as a competing events. Multiple imputation was performed for missing variables to reduce bias. Nomogram was developed to estimate 1-year cumulative incidence of transformation to blast phase. Results: The median age at the start of TKI therapy was 49 years (range, 15.1-86.4) with a median follow-up of 146 months (range, 5.3-253.9) (standard-dose imatinib, 231 months; dasatinib 137 months; nilotinib 138 months) (Table 1). Overall, the incidence of transformation to blast phase was observed in 8 patients during frontline TKI therapy; 4 patients received imatinib; and 4 patients received second-generation TKIs (1 patient, dasatinib; 3 patients, nilotinib). Competing risk regression identified percentage of blasts in peripheral blood and bone marrow, and standard-dose imatinib therapy as prognostic factors for transformation to blast phase during frontline TKI therapy. The 1-year cumulative incidence of transformation rates were 4% and 1% in the imatinib and second-generation TKI groups, respectively; the 5-year cumulative incidence rates were 5% and 1%, respectively (P=0.043 by Gray's test). The nomogram was developed for the risk calculations for 1-year transformation to blast phase (Figure 1). Conclusion: The incidence of transformation to blast phase is rare in the era of TKI therapy. The nomogram helps physicians select optimal TKI therapy to prevent the transformation to blast phase. Given the dismal outcome of patients who progressed to blast phase, we propose frontline second-generation TKI therapy in patients with estimated 1-year cumulative incidence of transformation above 5% or higher. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Molecular Markers of Response to Anti-PD1 Therapy in Advanced Hepatocellular Carcinoma

Background & AimsSingle-agent anti-PD1 checkpoint inhibitors convey outstanding clinical benefits in a small fraction (∼20%) of patients with advanced hepatocellular carcinoma (aHCC) but the molecular mechanisms determining response are unknown. To fill this gap, we herein analyze the molecular and immune traits of aHCC in patients treated with anti-PD1. MethodsOverall, 111 tumor samples from patients with aHCC were obtained from 13 centers before systemic therapies. We performed molecular analysis and immune deconvolution using whole-genome expression data (n = 83), mutational analysis (n = 72), and histologic evaluation with an endpoint of objective response. ResultsAmong 83 patients with transcriptomic data, 28 were treated in frontline, whereas 55 patients were treated after tyrosine kinase inhibitors (TKI) either in second or third line. Responders treated in frontline showed upregulated interferon-γ signaling and major histocompatibility complex II–related antigen presentation. We generated an 11-gene signature (IFNAP), capturing these molecular features, which predicts response and survival in patients treated with anti-PD1 in frontline. The signature was validated in a separate cohort of aHCC and >240 patients with other solid cancer types where it also predicted response and survival. Of note, the same signature was unable to predict response in archival tissue of patients treated with frontline TKIs, highlighting the need for fresh biopsies before immunotherapy. ConclusionInterferon signaling and major histocompatibility complex–related genes are key molecular features of HCCs responding to anti-PD1. A novel 11-gene signature predicts response in frontline aHCC, but not in patients pretreated with TKIs. These results must be confirmed in prospective studies and highlights the need for biopsies before immunotherapy to identify biomarkers of response.

Chronic myeloid leukemia: 2022 update on diagnosis, therapy, and monitoring.

Chronic Myeloid Leukemia (CML) is a myeloproliferative neoplasm with an incidence of 1-2 cases per 100 000 adults. It accounts for approximately 15% of newly diagnosed cases of leukemia in adults. CML is characterized by a balanced genetic translocation, t (9;22) (q34;q11.2), involving a fusion of the Abelson gene (ABL1) from chromosome 9q34 with the breakpoint cluster region (BCR) gene on chromosome 22q11.2. This rearrangement is known as the Philadelphia chromosome. The molecular consequence of this translocation is the generation of a BCR::ABL1 fusion oncogene, which in turn translates into a BCR::ABL1 oncoprotein. Four tyrosine kinase inhibitors (TKIs), imatinib, dasatinib, bosutinib, and nilotinib are approved by the United States Food and Drug Administration for first-line treatment of newly diagnosed CML in chronic phase (CML-CP). Clinical trials with second generation TKIs reported significantly deeper and faster responses but had no impact on survival prolongation, likely because of the availability of effective TKIs salvage therapies for patients who have a cytogenetic relapse with frontline TKI therapy. For CML post failure on frontline therapy, second-line options include second and third generation TKIs. Although potent and selective, these TKIs exhibit unique pharmacological profiles and response patterns relative to different patient and disease characteristics, such as patients' comorbidities, disease stage, and BCR::ABL1 mutational status. Patients who develop the T315I "gatekeeper" mutation display resistance to all currently available TKIs except ponatinib, asciminib, and olverembatinib. Allogeneic stem cell transplantation remains an important therapeutic option for patients with CML-CP and failure (due to resistance) of at least two TKIs, and for all patients in advanced phase disease. Older patients who have a cytogenetic relapse post failure on all TKIs can maintain long-term survival if they continue a daily most effective/least toxic TKI, with or without the addition of non-TKI anti-CML agents (hydroxyurea, omacetaxine, azacitidine, decitabine, cytarabine, busulfan and others).

Treatment-free remission (TFR) in patients with chronic myeloid leukemia (CML) following the discontinuation of tyrosine kinase inhibitors.

7050 Background: Tyrosine kinase inhibitors (TKIs) discontinuation in patients (pts) with CML is increasingly considered. We evaluated the outcome of pts with CML who discontinued TKIs and determined the factors associated with differences in the success rates of TFR. Methods: We reviewed data from 284 pts with CML treated with TKIs at our institution between October 1999 and February 2017 and who subsequently discontinued therapy. Major molecular response (MMR) was defined as a BCR-ABL1/ABL1 transcripts ratio ≤0.1% as determined by real time (RT)-PCR, MR4 as a ratio ≤0.01% IS, and MR4.5 as a ratio ≤0.0032%. TFR failure was defined as the loss of MMR on any single test. We analyzed TFR rates according to duration and depth of response and conducted a multivariate analysis for factors associated with loss of MMR. Results: Median age was 63 years (range, 25-93). 199 pts (70%) had electively discontinued their TKI while 70 pts (24%) stopped therapy because of adverse events. 92 pts (32%) had switched ≥1 TKI prior to discontinuation due to drug intolerance or resistance. The median time from the initiation of frontline TKI to discontinuation was 117 months (range, 16-242). The median duration of MR4 and MR4.5 before TKI discontinuation was 74 months (range, 2-207) and 64 months (range, 0-207), respectively. At a median follow-up of 36 months (95% CI, 32-40) after TKI discontinuation, 53 pts (19%) lost MMR, translating into a 5-year TFR rate of 79%. 50 pts (94%) resumed TKI therapy and, among 47 evaluable pts, all but one pt regained MMR, with 41 pts (88%) achieving MR4.5. The estimated 5-year TFR rates were 91%, 76% and 70% in pts achieving MR4.5 for ≥6 years, between 5 and 6 years, and &lt; 5 years, respectively (P &lt; 0.0001). The estimated 5-year TFR rates were higher with MR4 and MR4.5 ≥5 years, compared with MR4 &lt; 5 years (87% vs 92% vs 64%; P &lt; 0.0001). Pts who remained on their frontline TKI at the time of discontinuation had a 5-year TFR rate of 82%, compared with 75% and 72% among pts who switched to a second line TKI or beyond because of intolerance or resistance, respectively (P = 0.417). TFR rates did not vary according to the type of frontline TKI used (P = 0.761). By multivariate analysis, only durations in MR4 or MR4.5 ≥5 years before stopping treatment were associated with a lower risk of loss of MMR, with hazard ratios of 0.37 (95% CI, 0.18-0.76; P = 0.007) and 0.20 (95% CI, 0.09-0.45; P &lt; 0.0001), respectively. We evaluated the impact of the frequency of molecular monitoring on the success rate of TFR. The estimated 5-year TFR rate was 79% for pts monitored monthly compared with 85% for pts monitored every 6-8 weeks following discontinuation (P = 0.263). Conclusions: Our findings suggest that achieving MR4 for ≥5 years was associated with a very high probability of maintaining TFR, and that less frequent molecular monitoring could be more cost-effective without any negative impact on outcomes.