Increased expression of protease-activated receptor 1 (PAR-1) in human leukemias

Protease-activated receptor 1 (PAR-1) is a G-protein-coupled receptor that is overexpressed in solid tumors, being associated with several pro-tumoral responses including primary growth, invasion, metastasis and angiogenesis. Expression of PAR-1 in human leukemic cell lines is reported but the status of its expression in human leukemic patients is currently unknown. In this study we evaluated the expression pattern of PAR-1 in patients with the four main types of leukemia - chronic lymphocytic leukemia subtype B (B-CLL), acute lymphoblastic leukemia subtype B (B-ALL), acute myeloid leukemia (AML) and chronic myeloid leukemia (CML). Flow cytometry analyses show that lymphocytes from B-CLL patients express this receptor at similar levels to healthy individuals. On the other hand, it was observed a significant increase in PAR-1 expression in B-ALL lymphocytes as compared to B-CLL and healthy donors. Flow cytometric and real-time PCR demonstrated a significant increase in PAR-1 expression in granulocytes from CML patients in blast phase (CML-BP) but not in chronic phase (CML-CP) as compared to healthy donors. Finally, a significant increase in PAR-1 expression has been also observed in blasts from AML (subtypes M4 and M5) patients, as compared to monocytes or granulocytes from healthy donors. We conclude that PAR-1 might play an important biological role in aggressive leukemias and might offer additional strategies for the development of new therapies. (C) 2010 Elsevier Inc. All rights reserved.

Skin and oral lesions associated to imatinib mesylate therapy

Imatinib mesylate is a tyrosine kinase inhibitor used to treat chronic myeloid leukemia (CML) throughout all the phases of the disease. In most cases, this drug is well tolerated; however, some cases experience side effects. Skin rashes and oral lesions are uncommon and appear to be dose-dependent. The authors report two cases of CML Ph(+) in chronic phase patients who presented skin and oral lesions probably induced by imatinib therapy.

Is p190 bcr-abl rearrangement necessary for acute transformation in some p210 CML of childhood?

Chronic myeloid leukemia (CML) is a rare disease in childhood which is almost exclusively associated with bcr-abl p210 (M-bcr) rearrangements. It has been suggested that co-expression of p 190 and p210 may be a pathway of CML progression in adult patients. We report two cases of pediatric patients with a diagnosis of CML who presented co-expression of the p210 and p190 transcripts during progression to the blastic phase. The present data suggest that p190 may be a secondary event in at least some cases of childhood CML, suggesting an association with progression to a blastic crisis in these patients. (c) 2008 Elsevier Ltd. All rights reserved.

Large-scale imatinib dose-concentration-effect study in CML patients under routine care conditions.

This observational study analyzed imatinib pharmacokinetics and response in 2478 chronic myeloid leukemia (CML) patients. Data were obtained through centralized therapeutic drug monitoring (TDM) at median treatment duration of ≥2 years. First, individual initial trough concentrations under 400mg/day imatinib starting dose were estimated. Second, their correlation (C^min(400mg)) with reported treatment response was verified. Low imatinib levels were predicted in young male patients and those receiving P-gp/CYP3A4 inducers. These patients had also lower response rates (7% lower 18-months MMR in male, 17% lower 1-year CCyR in young patients, Kaplan-Meier estimates). Time-point independent multivariate regression confirmed a correlation of individual C^min(400mg) with response and adverse events. Possibly due to confounding factors (e.g. dose modifications, patient selection bias), the relationship seemed however flatter than previously reported from prospective controlled studies. Nonetheless, these observational results strongly suggest that a subgroup of patients could benefit from early dosage optimization assisted by TDM, because of lower imatinib concentrations and lower response rates.

Pharmacokinetic (PK)-based dosage individualization of imatinib: evaluation of efficiency and clinical usefulness

Background: Retrospective analyses suggest that personalized PK-based dosage might be useful for imatinib, as treatment response correlates with trough concentrations (Cmin) in cancer patients. Our objectives were to improve the interpretation of randomly measured concentrations and to confirm its efficiency before evaluating the clinical usefulness of systematic PK-based dosage in chronic myeloid leukemia patients. Methods and Results: A Bayesian method was validated for the prediction of individual Cmin on the basis of a single random observation, and was applied in a prospective multicenter randomized controlled clinical trial. 28 out of 56 patients were enrolled in the systematic dosage individualization arm and had 44 follow-up visits (their clinical follow-up is ongoing). PK-dose-adjustments were proposed in 39% having predicted Cmin significantly away from the target (1000 ng/ml). Recommendations were taken up by physicians in 57%, patients were considered non-compliant in 27%. Median Cmin at study inclusion was 754 ng/ml and differed significantly from the target (p=0.02, Wilcoxon test). On follow-up, Cmin was 984 ng/ml (p=0.82) in the compliant group. CV decreased from 46% to 27% (p=0.02, F-test). Conclusion: PK-based (Bayesian) dosage adjustment is able to bring individual drug exposure closer to a given therapeutic target. Its influence on therapeutic response remains to be evaluated.

Importance of influx and efflux systems and xenobiotic metabolizing enzymes in intratumoral disposition of anticancer agents.

In this review, intratumoral drug disposition will be integrated into the wide range of resistance mechanisms to anticancer agents with particular emphasis on targeted protein kinase inhibitors. Six rules will be established: 1. There is a high variability of extracellular/intracellular drug level ratios; 2. There are three main systems involved in intratumoral drug disposition that are composed of SLC, ABC and XME enzymes; 3. There is a synergistic interplay between these three systems; 4. In cancer subclones, there is a strong genomic instability that leads to a highly variable expression of SLC, ABC or XME enzymes; 5. Tumor-expressed metabolizing enzymes play a role in tumor-specific ADME and cell survival and 6. These three systems are involved in the appearance of resistance (transient event) or in the resistance itself. In addition, this article will investigate whether the overexpression of some ABC and XME systems in cancer cells is just a random consequence of DNA/chromosomal instability, hypo- or hypermethylation and microRNA deregulation, or a more organized modification induced by transposable elements. Experiments will also have to establish if these tumor-expressed enzymes participate in cell metabolism or in tumor-specific ADME or if they are only markers of clonal evolution and genomic deregulation. Eventually, the review will underline that the fate of anticancer agents in cancer cells should be more thoroughly investigated from drug discovery to clinical studies. Indeed, inhibition of tumor expressed metabolizing enzymes could strongly increase drug disposition, specifically in the target cells resulting in more efficient therapies.

Impact of additional cytogenetic aberrations at diagnosis on prognosis of CML: long-term observation of 1151 patients from the randomized CML Study IV.

The prognostic relevance of additional cytogenetic findings at diagnosis of chronic myeloid leukemia (CML) is unclear. The impact of additional cytogenetic findings at diagnosis on time to complete cytogenetic (CCR) and major molecular remission (MMR) and progression-free (PFS) and overall survival (OS) was analyzed using data from 1151 Philadelphia chromosome-positive (Ph(+)) CML patients randomized to the German CML Study IV. At diagnosis, 1003 of 1151 patients (87%) had standard t(9;22)(q34;q11) only, 69 patients (6.0%) had variant t(v;22), and 79 (6.9%) additional cytogenetic aberrations (ACAs). Of these, 38 patients (3.3%) lacked the Y chromosome (-Y) and 41 patients (3.6%) had ACAs except -Y; 16 of these (1.4%) were major route (second Philadelphia [Ph] chromosome, trisomy 8, isochromosome 17q, or trisomy 19) and 25 minor route (all other) ACAs. After a median observation time of 5.3 years for patients with t(9;22), t(v;22), -Y, minor- and major-route ACAs, the 5-year PFS was 90%, 81%, 88%, 96%, and 50%, and the 5-year OS was 92%, 87%, 91%, 96%, and 53%, respectively. In patients with major-route ACAs, the times to CCR and MMR were longer and PFS and OS were shorter (P < .001) than in patients with standard t(9;22). We conclude that major-route ACAs at diagnosis are associated with a negative impact on survival and signify progression to the accelerated phase and blast crisis.

Impact of Balanced or Unbalanced Karyotype At Diagnosis On Prognosis of CML: Long-Term Observation From 1346 Patients of the Randomized CML Study IV

Introduction: Acquired genetic instability in chronic myeloid leukemia (CML) as a consequence of the translocation t(9;22)(q34;q11) and the resulting BCR-ABL fusion causes the continuous acquisition of additional chromosomal aberrations and mutations and thereby progression to accelerated phase (AP) and blast crisis (BC). At least 10% of patients in chronic phase (CP) CML show additional alterations at diagnosis. This proportion rises during the course of the disease up to 80% in BC. Acquisition of chromosomal changes during treatment is considered as a poor prognostic indicator, whereas the impact of chromosomal aberrations at diagnosis depends on their type. Patients with major route additional chromosomal alterations (major ACA: +8, i(17)(q10), +19, +der(22)t(9;22)(q34;q11) have a worse outcome whereas patients with minor route ACA show no difference in overall survival (OS) and progression-free survival (PFS) compared to patients with the standard translocation, a variant translocation or the loss of the Y chromosome (Fabarius et al., Blood 2011). However, the impact of balanced vs. unbalanced (gains or losses of chromosomes or chromosomal material) karyotypes at diagnosis on prognosis of CML is not clear yet. Patients and methods: Clinical and cytogenetic data of 1346 evaluable out of 1544 patients with Philadelphia and BCR-ABL positive CP CML randomized until December 2011 to the German CML-Study IV, a randomized 5-arm trial to optimize imatinib therapy by combination, or dose escalation and stem cell transplantation were investigated. There were 540 females (40%) and 806 males (60%). Median age was 53 years (range, 16-88). The impact of additional cytogenetic aberrations in combination with an unbalanced or balanced karyotype at diagnosis on time to complete cytogenetic and major molecular remission (CCR, MMR), PFS and OS was investigated. Results: At diagnosis 1174/1346 patients (87%) had the standard t(9;22)(q34;q11) only and 75 patients (6%) had a variant t(v;22). In 64 of 75 patients with t(v;22), only one further chromosome was involved in the translocation; In 8 patients two, in 2 patients three, and in one patient four further chromosomes were involved. Ninety seven patients (7%) had additional cytogenetic aberrations. Of these, 44 patients (3%) lacked the Y chromosome (-Y) and 53 patients (4%) had major or minor ACA. Thirty six of the 53 patients (2.7%) had an unbalanced karyotype (including all patients with major route ACA and patients with other unbalanced alterations like -X, del(1)(q21), del(5)(q11q14), +10, t(15;17)(p10;p10), -21), and 17 (1.3%) a balanced karyotype with reciprocal translocations [e.g. t(1;21); t(2;16); t(3;12); t(4;6); t(5;8); t(15;20)]. After a median observation time of 5.6 years for patients with t(9;22), t(v;22), -Y, balanced and unbalanced karyotype with ACA median times to CCR were 1.05, 1.05, 1.03, 2.58 and 1.51 years, to MMR 1.31, 1.51, 1.65, 2.97 and 2.07 years. Time to CCR and MMR was longer in patients with balanced karyotypes (data statistically not significant). 5-year PFS was 89%, 78%, 87%, 94% and 69% and 5-year OS 91%, 87%, 89%, 100% and 73%, respectively. In CML patients with unbalanced karyotype PFS (p<0.001) and OS (p<0.001) were shorter than in patients with standard translocation (or balanced karyotype; p<0.04 and p<0.07, respectively). Conclusion: We conclude that the prognostic impact of additional cytogenetic alterations at diagnosis of CML is heterogeneous and consideration of their types may be important. Not only patients with major route ACA at diagnosis of CML but also patients with unbalanced karyotypes identify a group of patients with shorter PFS and OS as compared to all other patients. Therefore, different therapeutic options such as intensive therapy with the most potent tyrosine kinase inhibitors or stem cell transplantation are required.

Imatinib plasma concentrations variability in oncologic patients

Imatinib (Glivec®) has transformed the treatment and short-term prognosis of chronic myeloid leukemia (CML) and gastrointestinal stromal tumor (GIST). However, the treatment must be taken indefinitely, it is not devoid of inconvenience and toxicity. Moreover, resistance or escape from disease control occurs in a significant number of patients. Imatinib is a substrate of the cytochromes P450 CYP3A4/5 and of the multidrug transporter P-glycoprotein (product of the MDR1 gene). Considering the large inter-individual differences in the expression and function of those systems, the disposition and clinical activity of imatinib can be expected to vary widely among patients, calling for dosage individualization. The aim of this exploratory study was to determine the average pharmacokinetic parameters characterizing the disposition of imatinib in the target population, to assess their inter-individual variability, and to identify influential factors affecting them. A total of 321 plasma concentrations, taken at various sampling times after the latest dose, were measured in 59 patients receiving Glivec at diverse regimens, using a validated HPLC-UV method developed for this study. The results were analyzed by non-linear mixed effect modeling (NONMEM). A one-compartment model with first-order absorption appeared appropriate to describe the data, with an average apparent clearance of 12.4 l/h, a distribution volume of 268 l and an absorption constant of 0.47 h-1. The clearance was affected by body weight, age and sex. No influences of interacting drugs were found. DNA samples were used for pharmacogenetic explorations. At present, only the MDR1 polymorphism has been assessed and seems to affect the pharmacokinetic parameters of imatinib. Large inter-individual variability remained unexplained by the demographic covariates considered, both on clearance (40 %) and distribution volume (71 %). Together with intra-patient variability (34 %), this translates into an 8-fold width of the 90 %-prediction interval of plasma concentrations expected under a fixed dosing regimen. This is a strong argument to further investigate the possible usefulness of a therapeutic drug monitoring program for imatinib. It may help to individualize the dosing regimen before overt disease progression or observation of treatment toxicity, thus improving both the long-term therapeutic effectiveness and tolerability of this drug.

Imatinib plasma concentrations variability in oncologic patients

The anticancer drug imatinib has transformed the treatment and prognosis of chronic myeloid leukemia and gastrointestinal stromal tumor. However, the treatment must be taken indefinitely and is not devoid of inconveniences and toxicity. Moreover, resistance or escape from disease control are occurring. Considering the large interindividual differences in the function of the enzymatic and transport systems involved in imatinib disposition, exposure to this drug can be expected to vary widely among patients. This book describes an observational clinical trial aiming at exploring the influence of these covariates on imatinib pharmacokinetics and assessing the interindividual variability of the pharmacokinetic parameters of the drug. A large interindividual variability was observed, together with some preliminary concentration-effect relationships. These elements are arguments to further investigate the potential benefit of a therapeutic drug monitoring program to optimize the use of imatinib in patients. Such results should be especially useful to clinical oncologists or scientists involved in clinical oncology research.

Clinical consequences of imatinib plasma concentrations variability in hemato-oncologic patients

Background: Imatinib has revolutionized the treatment of chronic myeloid leukemia (CML) and gastrointestinal stromal tumors (GIST). Considering the large inter-individual differences in the function of the systems involved in its disposition, exposure to imatinib can be expected to vary widely among patients. This observational study aimed at describing imatinib pharmacokinetic variability and its relationship with various biological covariates, especially plasma alpha1-acid glycoprotein (AGP), and at exploring the concentration-response relationship in patients. Methods: A population pharmacokinetic model (NONMEM) including 321 plasma samples from 59 patients was built up and used to derive individual post-hoc Bayesian estimates of drug exposure (AUC; area under curve). Associations between AUC and therapeutic response or tolerability were explored by ordered logistic regression. Influence of the target genotype (i.e. KIT mutation profile) on response was also assessed in GIST patients. Results: A one-compartment model with first-order absorption appropriately described the data, with an average oral clearance of 14.3 L/h (CL) and volume of distribution of 347 L (Vd). A large inter-individual variability remained unexplained, both on CL (36%) and Vd (63%), but AGP levels proved to have a marked impact on total imatinib disposition. Moreover, both total and free AUC correlated with the occurrence and number of side effects (e.g. OR 2.9±0.6 for a 2-fold free AUC increase; p<0.001). Furthermore, in GIST patients, higher free AUC predicted a higher probability of therapeutic response (OR 1.9±0.5; p<0.05), notably in patients with tumor harboring an exon 9 mutation or wild-type KIT, known to decrease tumor sensitivity towards imatinib. Conclusion: The large pharmacokinetic variability, associated to the pharmacokinetic-pharmacodynamic relationship uncovered are arguments to further investigate the usefulness of individualizing imatinib prescription based on TDM. For this type of drug, it should ideally take into consideration either circulating AGP concentrations or free drug levels, as well as KIT genotype for GIST.

Frequent clonal loss of heterozygosity but scarcity of microsatellite instability at chromosomal breakpoint cluster regions in adult leukemias.

Microsatellites are important highly polymorphic genetic markers dispersed in the human genome. Using a panel of 22 (CA)n repeat microsatellite markers mapped to recurrent breakpoint cluster regions specifically involved in leukemia, we investigated 114 adult leukemias (25 acute lymphocytic leukemia [ALL], 32 acute myeloid leukemia [AML], 36 chronic lymphocytic leukemia [CLL], and 21 chronic myeloid leukemia [CML] in chronic phase) for somatic mutations at these loci. In each patient, DNA from fresh leukemia samples was analyzed alongside normal constitutive DNA from buccal epithelium. We detected loss of heterozygosity (LOH) in 81 of 114 patients (ALL 16/25, AML 25/32, CLL 30/36, CML 10/21). Deletions were most often seen in ALL at 11q23 and 19p13; in AML at 8q22 and 11q23; in CLL at 13q14.3, 11q13, and 11q23; and in CML at 3q26. Only six deletions were reported in 74 karyotypes analyzed, whereas in these same cases, 91 LOH events were detected by microsatellites. Of 26 leukemias with a normal karyotype, 16 nevertheless showed at least one LOH by microsatellite analysis. Replication errors were found in 10 of 114 patients (8.8%). Thus, microsatellite instability is rare in leukemia in contrast to many solid tumors. Our findings suggest that in adult leukemia, LOH may be an important genetic event in addition to typical chromosomal translocations. LOH may point to the existence of tumor suppressor genes involved in leukemogenesis to a degree that has hitherto been underestimated.

Therapeutic Drug Monitoring (TDM) of Imatinib: Effectiveness of Bayesian dose adjustment for CML patients enrolled in the Imatinib Concentration Monitoring (I-COME) study

Introduction: As imatinib pharmacokinetics are highly variable, plasma levels differ largely between patients under the same dosage. Retrospective studies in chronic myeloid leukemia (CML) patients showed significant correlations between low levels and suboptimal response, as well as between high levels and poor tolerability. Monitoring of trough plasma levels, targeting 1000 μg/L and above, is thus increasingly advised. Our study was launched to assess prospectively the clinical usefulness of systematic imatinib TDM in CML patients. This preliminary analysis addresses the appropriateness of the dosage adjustment approach applied in this study, which targets the recommended trough level and allows an interval of 4-24 h after last drug intake for blood sampling. Methods: Blood samples from the first 15 patients undergoing 1st TDM were obtained 1.5-25 h after last dose. Imatinib plasma levels were measured by LC-MS/MS and the concentrations were extrapolated to trough based on a Bayesian approach using a population pharmacokinetic model. Trough levels were predicted to differ significantly from the target in 12 patients (10 <750 μg/L; 2 >1500 μg/L along with poor tolerance) and individual dose adjustments were proposed. 8 patients underwent a 2nd TDM cycle. Trough levels of 1st and 2nd TDM were compared, the sample drawn 1.5 h after last dose (during distribution phase) was excluded from the analysis. Results: Individual dose adjustments were applied in 6 patients. Observed concentrations extrapolated to trough ranged from 360 to 1832 μg/L (median 725; mean 810, CV 52%) on 1st TDM and from 720 to 1187 μg/L (median 950; mean 940, CV 18%) on 2nd TDM cycle. Conclusions: These preliminary results suggest that TDM of imatinib using a Bayesian interpretation is able to target the recommended trough level of 1000 μg/L and to reduce the considerable differences in trough level exposure between patients (with CV decreasing from 52% to 18%). While this may simplify blood collection in daily practice, as samples do not have to be drawn exactly at trough, the largest possible interval to last drug intake yet remains preferable to avoid sampling during distribution phase leading to biased extrapolation. This encourages the evaluation of the clinical benefit of a routine TDM intervention in CML patients, which the randomized Swiss I-COME trial aims to.

Cataractogenesis after total body irradiation.

PURPOSE: To evaluate the prognostic factors and the ophthalmologic follow-up on cataract formation following total body irradiation (TBI) prior to bone marrow transplantation (BMT). METHODS AND MATERIALS: Between 1980 and 1992, 494 patients were referred to our department for TBI prior to BMT. The mean age was 32 +/- 11 (median: 32, range: 2-63) years and the male to female ratio was 1.6 (304:190). The majority of patients were treated for acute leukemia (lymphoblastic, n = 177, 36%; or nonlymphoblastic , n = 139, 28%); 80 (16%) for chronic myeloid leukemia, 60 (12%) for non-Hodgkin's lymphoma, 23 (5%) for multiple myeloma, and 15 (3%) for other malignancies. Two hundred and fifty-four (51%) patients were grafted in the first complete remission (CR), 118 (24%) in second CR. Allogenic BMT was performed in 210 (43%) patients, and autologous BMT in 284 (57%). Methotrexate combined to steroids (n = 47, 22%) or to cyclosporine (n = 163, 78%) was administered for graft-versus-host disease (GvHD) prophylaxis. In 188 patients (38%), heparin was used in the prevention of veno-occlusive disease (VOD) of the liver. Furthermore, steroid administration was registered in 223 (45%). The conditioning chemotherapy consisted of cyclophosphamide (Cy) alone in 332 (67%) patients. Total-body irradiation was administered either in single dose (STBI; 10 Gy in 1 day, n = 291) or in six fractions (FTBI; 12 Gy over 3 consecutive days, n = 203) before BMT. The mean instantaneous dose rate was 0.0574 +/- 0.0289 Gy/min (0.024-0.1783). It was < 0.048 Gy/min in 157 patients (LOW group), > or = 0.048 Gy/min and <0.09 Gy/min in 301 patients (MEDIUM group), and > or = 0.09 Gy/min in 36 patients (HIGH group). RESULTS: When considering all patients, 42 (8.5%) patients developed cataracts after 13 to 72 months (median: 42 months) with a 5-year estimated cataract incidence (ECI) of 23%. Thirty-three (11.3%) out of 291 patients in the STBI group, and 9 (4.4%) out of 203 patients in the FTBI group developed cataracts with 5-year estimated incidences of 34 and 11%, respectively (p = 0.0004). Seven (19.4%) out of 36 patients in the HIGH group, 33 (10.9%) out of 301 in the MEDIUM group, and 2 (1.2%) out of 157 in the LOW group developed cataracts with respective 5-year cataract incidences of 54%, 30%, and 3.5% (HIGH vs. MEDIUM, p = 0.07; MEDIUM vs. LOW, p = 0.0001; HIGH vs. LOW, p < 0.0001). On the other hand, patients who received heparin as prophylactic treatment against VOD of the liver had less cataracts than those who did not receive (5-year ECI of 16% vs. 28%, respectively; p = 0.01). There was no statistically significant difference in terms of 5-year ECI according to age, sex, administration of steroids, GvHD prophylaxis, type of BMT, or previous cranial radiotherapy in children. Multivariate analysis revealed that the instantaneous dose rate (p = 0.001), and the administration of heparin against VOD (p = 0.05) were the two independent factors influencing the cataract incidence, while age, fractionation, and use of steroids were not. Among the 42 patients who developed cataracts, 38 had bilateral extracapsular cataract extraction and intraocular lens implantation, and only 4 (10%) developed secondary cataracts in a median follow-up period of 39 months. CONCLUSION: Among the abovementioned TBI parameters, high instantaneous dose rate seems to be the main risk factor of cataract formation, and the administration of heparin appears to have a protective role in cataractogenesis. On the other hand, ionizing radiation seems to have a protective effect on posterior capsule opacification following extracapsular cataract extraction and intraocular lens implantation.

Clinical usefulness of therapeutic concentration monitoring for imatinib dosage individualization: Results from the randomized controlled I-COME Trial

Introduction: Imatinib trough plasma concentrations (Cmin) have been correlated with treatment response in chronic myeloid leukemia (CML) patients. The use of Cmin monitoring for optimizing imatinib dosage (therapeutic drug monitoring [TDM]) is therefore proposed for patients with unsatisfying response or tolerance ("rescue TDM"). A cycle of "routine TDM" for dosage individualization could also be beneficial to prevent unfavorable events, yet its clinical usefulness has not been evaluated. We aimed to assess prospectively whether a "routine TDM" intervention targeting imatinib Cmin of 1000 ng/mL (tolerance, 750-1500 ng/mL) could improve efficacy, tolerance, and persistence on treatment compared with "rescue TDM" use only. Patients (or Materials) and Methods: The Swiss Imatinib COncentration Monitoring Evaluation (I-COME) study was a multicenter randomized controlled trial (ISRCTN31181395). Adult patients in chronic or accelerated phase CML receiving imatinib ≤5 years were eligible. Patients were randomly (1:1) allocated to receive "routine TDM" intervention or to serve as controls with access only to "rescue TDM". All had 1-year follow-up. The primary endpoint was a combined efficacy-safety outcome (failure- and toxicity-free survival without imatinib discontinuation), analyzed in intention-to-treat. Results: Among 56 CML recruited patients, 55 had their molecular and cytogenetic response measured. 14/27 of patients receiving "routine TDM" (52% [33%-71%]) remained event-free versus 16/28 of control patients with "rescue TDM" only (57% [39%-75%]; P=0.69). In the "routine TDM" group, dosage recommendations were adopted entirely in 50% of patients (median Cmin at study end, 895 ng/mL; CV = 33%). These patients had fewer unfavorable events (28% [5%-52%]) compared with patients not receiving the advised dosage (77% [54%-99%]; P = 0.03; median Cmin at study end, 648 ng/mL; CV = 38%). Conclusion: This first prospective target concentration intervention trial could not formally demonstrate a benefit of "routine TDM" of imatinib, especially due to a small patient number and limited prescriber's adherence to dosage recommendations. Nevertheless, the patients receiving the advised dosage more often met target concentrations and the combined outcome (efficacy, tolerance, and persistence). A cycle of routine TDM could thus be favorable, at least in patients eligible for dosage adjustment. Its usefulness should, however, be further confirmed in larger trials.