Anti-tumor activity of the MDM2-TP53 inhibitor BI-907828 in dedifferentiated liposarcoma patient-derived xenograft models harboring MDM2 amplification.

PURPOSE: Dedifferentiated liposarcoma (DDLPS) is a soft tissue malignancy characterized by amplification of the mouse double minute 2 homolog (MDM2) gene. MDM2 is a negative regulator of tumor protein 53 (TP53). We tested the in vivo efficacy of BI-907828, a small molecule inhibitor of the MDM2-TP53 interaction, in two DDLPS patient-derived xenografts (PDX). METHODS: Partially immunodeficient mice were bilaterally engrafted with UZLX-STS3 (n = 24) and UZLX-STS5 (n = 24) human DDLPS tissue harboring MDM2 amplifications. Mice were grouped as follows: (a) vehicle (0.5% hydroxyethylcellullose) 10 ml/kg daily per os (p.o.); (b) doxorubicin 5 mg/kg weekly intraperitoneally (i.p.); (c) BI-907828 2.5 mg/kg daily p.o. and (d) BI-907828 10 mg/kg daily p.o. The treatment lasted for 15 days, all mice treated with BI-907828 were followed for 37 days post-treatment. Efficacy was assessed by tumor volume and histopathological evaluation. RESULTS: The 15-day treatment with 2.5 mg/kg and 10 mg/kg BI-907828 significantly inhibited tumor growth in UZLX-STS5 and -STS3 (p < 0.0001 compared to control for both models). All UZLX-STS5 and -STS3 tumors treated with BI-907828 decreased in size during treatment, and BI-907828-treated UZLX-STS5 tumors even disappeared completely. During the follow-up period, no tumor regrowth was observed in the UZLX-STS5 model and both doses of BI-907828 led to a pathological complete response, whereas a dose-dependent regrowth was seen in the UZLX-STS3 model. CONCLUSION: BI-907828 showed significant anti-tumor activity in DDLPS PDX harboring MDM2 amplifications, providing a strong rationale for early clinical testing of BI-907828 in a DDLPS patient population.

Activity and safety of crizotinib in patients with alveolar soft part sarcoma with rearrangement of TFE3: European Organization for Research and Treatment of Cancer (EORTC) phase II trial 90101 'CREATE'.

Background: Alveolar soft part sarcoma (ASPS) is an orphan malignancy associated with a rearrangement of transcription factor E3 (TFE3), leading to abnormal MET gene expression. We prospectively assessed the efficacy and safety of the MET tyrosine kinase inhibitor crizotinib in patients with advanced or metastatic ASPS. Patients and methods: Eligible patients with reference pathology-confirmed ASPS received oral crizotinib 250 mg bd. By assessing the presence or absence of a TFE3 rearrangement, patients were attributed to MET+ and MET- sub-cohorts. The primary end point was the objective response rate (ORR) according to local investigator. Secondary end points included duration of response, disease control rate (DCR), progression-free survival (PFS), progression-free rate, overall survival (OS) and safety. Results: Among 53 consenting patients, all had a centrally confirmed ASPS and 48 were treated. A total of 45 were eligible, treated and assessable. Among 40 MET+ patients, 1 achieved a confirmed partial response (PR) that lasted 215 days and 35 had stable disease (SD) as best response (ORR: 2.5%, 95% CI 0.6% to 80.6%). Further efficacy end points in MET+ cases were DCR: 90.0% (95% CI 76.3% to 97.2%), 1-year PFS rate: 37.5% (95% CI 22.9% to 52.1%) and 1-year OS rate: 97.4% (95% CI 82.8% to 99.6%). Among 4 MET- patients, 1 achieved a PR that lasted 801 days and 3 had SD (ORR: 25.0%, 95% CI 0.6% to 80.6%) for a DCR of 100% (95% CI 39.8% to 100.0%). The 1-year PFS rate in MET- cases was 50% (95% CI 5.8% to 84.5%) and the 1-year OS rate was 75% (95% CI 12.8% to 96.1%). One patient with unknown MET status due to technical failure achieved SD but stopped treatment due to progression after 17 cycles. The most common crizotinib-related adverse events were nausea [34/48 (70.8%)], vomiting [22/48 (45.8%)], blurred vision [22/48 (45.8%)], diarrhoea (20/48 (41.7%)] and fatigue [19/48 (39.6%)]. Conclusion: According to European Organization for Research and Treatment of Cancer (EORTC) efficacy criteria for soft tissue sarcoma, our study demonstrated that crizotinib has activity in TFE3 rearranged ASPS MET+ patients. Clinical trial number: EORTC 90101, NCT01524926.

Activity and safety of crizotinib in patients with advanced clear-cell sarcoma with MET alterations: European Organization for Research and Treatment of Cancer phase II trial 90101 'CREATE'.

BACKGROUND: Clear-cell sarcoma (CCSA) is an orphan malignancy, characterized by a specific t(12;22) translocation, leading to rearrangement of the EWSR1 gene and overexpression of MET. We prospectively investigated the efficacy and safety of the tyrosine kinase inhibitor crizotinib in patients with advanced or metastatic CCSA. PATIENTS AND METHODS: Patients with CCSA received oral crizotinib 250 mg twice daily. Primary end point was objective response rate (ORR), secondary end points included duration of response, disease control rate (DCR), progression-free survival (PFS), progression-free rate (PFR), overall survival (OS), OS rate and safety. The study design focused on MET+ disease with documented rearrangement of the EWSR1 gene by fluorescence in situ hybridization. RESULTS: Among 43 consenting patients with the local diagnosis of CCSA, 36 had centrally confirmed CCSA, 28 of whom were eligible, treated and assessable. Twenty-six out of the 28 patients had MET+ disease, of whom one achieved a confirmed partial response and 17 had stable disease (SD) (ORR 3.8%, 95% confidence interval: 0.1-19.6). Further efficacy end points in MET+ CCSA were DCR: 69.2% (48.2% to 85.7%), median PFS: 131 days (49-235), median OS: 277 days (232-442). The 3-, 6-, 12- and 24-month PFR was 53.8% (34.6-73.0), 26.9% (9.8-43.9), 7.7% (1.3-21.7) and 7.7% (1.3-21.7), respectively. Among two assessable MET- patients, one had stable disease and one had progression. The most common treatment-related adverse events were nausea [18/34 (52.9%)], fatigue [17/34 (50.0%)], vomiting [12/34 (35.3%)], diarrhoea [11/34 (32.4%)], constipation [9/34 (26.5%)] and blurred vision [7/34 (20.6%)]. CONCLUSIONS: The PFS with crizotinib in MET+ CCSA is similar to results achieved first-line in non-selected metastatic soft tissue sarcomas with single-agent doxorubicin. The PFS is similar to results achieved with pazopanib in previously treated sarcoma patients. CLINICAL TRIAL NUMBER: EORTC 90101, EudraCT number 2011-001988-52, NCT01524926.

Long-term results of treatment of advanced dermatofibrosarcoma protuberans (DFSP) with imatinib mesylate - The impact of fibrosarcomatous transformation.

BACKGROUND: Dermatofibrosarcoma protuberans (DFSP) is rare, infiltrating dermal neoplasm, characterized by indolent growth and low probability of metastases. The first effective systemic therapy in DFSP introduced into clinical practice was imatinib, demonstrating high activity in advanced cases. The aim of the study was to perform an analysis of patients with advanced DFSP treated with imatinib, with or without surgery, in routine clinical practice with long-term follow-up. PATIENTS AND METHODS: We analyzed the data of 31 Caucasian patients (14 male, 17 female; median age 56 years) with locally advanced/initially inoperable and/or metastatic DFSP who started therapy with imatinib at initial dose 800 mg daily between 12/2004 and 07/2014. All diagnoses were confirmed cytogenetically for the presence of specific COL1A1-PDGFB fusion. Median follow-up time was 5.3 years. RESULTS: Metastases were present in 15 cases (8 - lungs, 5 - soft tissue, 2 - lymph nodes). Fibrosarcomatous transformation (FS-DFSP) was confirmed in 16 patients (52%). 5-year progression-free survival (PFS) rate was 58% (median 6.8 years), 5-year overall survival (OS) rate was 64% (median time for OS was not reached). The shorter PFS and OS correlated with FS-DFSP and presence of metastatic disease. 5-year PFS rate was 93% for classic DFSP and 33% for FS-DFSP. The best overall responses were: 21 partial responses (68%, including 8 FS-DFSP, but the responses were shorter than for classic DFSP), 6 stable disease (19%) and 4 progressive diseases (13%). Thirteen patients (47%) underwent resection of residual disease and nine of them remained free of disease, although imatinib was discontinued. Median survival after progression on imatinib was 19 months, and longer survival were observed only in cases were rescue surgery/radiotherapy was possible. CONCLUSIONS: Our results indicate the long-term activity of imatinib in therapy of inoperable and/or metastatic cases of DFSP, including FS-DFSP. Some DFSP patients initially evaluated as unresectable/metastatic or necessitating mutilating surgery turned resectable after imatinib therapy and this rational approach leading to complete remission maybe potentially curative.

Pulmonary metastasis of a meningioma presenting as a solitary pulmonary nodule: 2 case reports.

Distant metastases of meningioma are rare, especially in grade 1 meningiomas. In a recent literature review, only 115 cases were found. In almost all published cases, the meningioma was treated several years before the metastasis was diagnosed. The lungs are the most frequent site of metastasis. We describe two patients treated for meningioma (one case grade 1, the other grade 3) who were referred to the Respiratory Oncology Unit because of the incidental finding of a pulmonary nodule on routine chest radiography. Both had undergone several neurosurgical procedures but the last operation was more than 7 years before in both cases. Positron emission tomography scan was suggestive of a malignant lung tumour. The lesions were surgically removed. Pathology confirmed meningioma in both cases with the same WHO grade, immunohistochemical and genetic profiles as the original meningioma. Both patients recovered well from thoracic surgery. The patient with grade 3 meningioma died three years later from intracranial recurrence. When a patient previously treated for meningioma develops a nodular lung lesion, metastasis of the meningioma should be in the differential diagnosis list. Because of the occurrence of distant metastasis even in grade I meningiomas, we suggest that the grading system should take into account genetic changes in the meningioma. Chromosome 1p and 14q losses possibly explain the aggressive behaviour of the grade 1 meningioma.

MiR-17-92 and miR-221/222 cluster members target KIT and ETV1 in human gastrointestinal stromal tumours.

BACKGROUND: Gastrointestinal stromal tumours (GIST) are characterised by high expression of KIT and ETV1, which cooperate in GIST oncogenesis. Our aim was to identify microRNAs that are deregulated in GIST, have a role in GIST pathogenesis, and could potentially be used as therapeutic tool. METHODS: Differentially expressed microRNAs between primary GIST (n=50) and gastrointestinal leiomyosarcomas (GI-LMS, n=10) were determined using microarrays. Selected microRNA mimics were transfected into GIST-882 and GIST-T1 cell lines to study the effects of microRNA overexpression on GIST cells. Luciferase reporter assays were used to establish regulation of target genes by selected microRNAs. RESULTS: MiR-17-92 and miR-221/222 cluster members were significantly (P<0.01) lower expressed in GIST vs GI-LMS and normal gastrointestinal control tissues. MiR-17/20a/222 overexpression in GIST cell lines severely inhibited cell proliferation, affected cell cycle progression, induced apoptosis and strongly downregulated protein and--to a lesser extent--mRNA levels of their predicted target genes KIT and ETV1. Luciferase reporter assays confirmed direct regulation of KIT and ETV1 by miR-222 and miR-17/20a, respectively. CONCLUSION: MicroRNAs that may have an essential role in GIST pathogenesis were identified, in particular miR-17/20a/222 that target KIT and ETV1. Delivering these microRNAs therapeutically could hold great potential for GIST management, especially in imatinib-resistant disease.

A critical overview on ticagrelor in acute coronary syndromes.

Until a few years ago, the mainstay of anti-platelet therapy in patients with acute coronary syndrome (ACS) was the combination of aspirin and clopidogrel, a P2Y12 receptor inhibitor. However, current clinical practice has now changed with the introduction of ticagrelor, a more potent cardiovascular drug than clopidogrel, without the limitations related to clopidogrel therapy. In this review, we provide a critical overview of ticagrelor in ACS, highlight the results with ticagrelor in several subgroups of patients and discuss the future trials.

Prognostic value of KIT/PDGFRA mutations in gastrointestinal stromal tumours (GIST): Polish Clinical GIST Registry experience.

BACKGROUND: Majority of gastrointestinal stromal tumours (GISTs) are characterised by KIT-immunopositivity and the presence of KIT/platelet-derived growth factor receptor alpha (PDGFRA) activating mutations. PATIENTS AND METHODS: Spectrum and frequency of KIT and PDGFRA mutations were investigated in 427 GISTs. Univariate and multivariate analysis of relapse-free survival (RFS) was conducted in relation to tumours' clinicopathologic features and genotype. RESULTS: Mutations were found in 351 (82.2%) cases, including 296 (69.3%) KIT and 55 (12.9%) PDGFRA isoforms. Univariate analysis revealed higher 5-year RFS rate in women (37.9%; P = 0.028) and in patients with gastric tumours (46.3%; P < 0.001). In addition a better 5-year RFS correlated with smaller tumour size ≤ 5 cm (62.7%; P < 0.001), tumours with mitotic index ≤ 5/50 high-power fields (60%; P < 0.001), and characterised by (very) low/moderate risk (70.2%; P = 0.006). Patients with GISTs bearing deletions encompassing KIT codons 557/558 had worse 5-year RFS rate (23.8%) than those with any other KIT exon 11 mutations (41.8%; P < 0.001) or deletions not involving codons 557/558 (33.3%; P = 0.007). Better 5-year RFS characterised patients with KIT exon 11 point mutations (50.7%) or duplications (40%). By multivariate analysis, tumours with PDGFRA mutations and KIT exon 11 point mutations/other than 557/558 deletions had lower risk of progression than with KIT exon 11 557/558 deletions (both Ps = 0.001). CONCLUSIONS: KIT/PDGFRA mutational status has prognostic significance for patients' outcome and may help in management of patients with GISTs.

1q gain and CDT2 overexpression underlie an aggressive and highly proliferative form of Ewing sarcoma.

Despite extensive characterization of the role of the EWS-ETS fusions, little is known about secondary genetic alterations and their clinical contribution to Ewing sarcoma (ES). It has been demonstrated that the molecular structure of EWS-ETS lacks prognostic value. Moreover, CDKN2A deletion and TP53 mutation, despite carrying a poor prognosis, are infrequent. In this scenario identifying secondary genetic alterations with a significant prevalence could contribute to understand the molecular mechanisms underlying the most aggressive forms of ES.We screened a 67 ES tumor set for copy number alterations by array comparative genomic hybridization. 1q gain (1qG), detected in 31% of tumor samples, was found markedly associated with relapse and poor overall and disease-free survival and demonstrated a prognostic value independent of classical clinical parameters. Reanalysis of an expression dataset belonging to an independent tumor set (n=37) not only validated this finding but also led us to identify a transcriptomic profile of severe cell cycle deregulation in 1qG ES tumors. Consistently, a higher proliferation rate was detected in this tumor subset by Ki-67 immunohistochemistry. CDT2, a 1q-located candidate gene encoding a protein involved in ubiquitin ligase activity and significantly overexpressed in 1qG ES tumors, was validated in vitro and in vivo proving its major contribution to this molecular and clinical phenotype. This integrative genomic study of 105 ES tumors in overall renders the potential value of 1qG and CDT2 overexpression as prognostic biomarkers and also affords a rationale for the application of already available new therapeutic compounds selectively targeting the protein-ubiquitin machinery.

Treatment of advanced dermatofibrosarcoma protuberans with imatinib mesylate with or without surgical resection.

BACKGROUND: Dermatofibrosarcoma protuberans (DFSP) is a rare soft tissue sarcoma of the skin characterized by the presence of specific COL1A1-PDGFB fusion protein, which appears as a consequence of the t(17;22) (q22;q13) translocation. OBJECTIVE: The aim of the study was to perform an analysis of patients with advanced DFSP treated with imatinib, with or without surgery, in clinical practice outside trials. PATIENTS AND METHODS: We analysed the data of 15 patients (6 male, 9 female; median age 56 years) with locally advanced/initially inoperable and/or metastatic DFSP treated with imatinib 400-800 mg daily between 12/2004 and 06/2009. All diagnoses were ascertained cytogenetically (fluorescent in situ hybridization). Median follow-up time was 16 months (range: 4-81). RESULTS: Metastases were present in six cases (two lungs, two soft tissue, two lymph nodes). Fibrosarcomatous transformation (FS-DFSP) was confirmed in seven patients (47%). A 2-year progression-free survival (PFS) rate was 60%, and a 2-year overall survival (OS) rate was 78% (median time for PFS/OS was not reached). The best overall responses were: 10 partial responses (67%, including 5 FS-DFSP-1 progressed during the follow-up), 2 stable diseases (13%) and 3 progressive diseases (20%). Seven patients (47%) underwent resection of residual disease and remained free of disease. CONCLUSIONS: We have confirmed the profound anti-tumour effect of imatinib in DFSP harbouring t(17;22) with long-term responses. Imatinib therapy may in some cases lead to tumour resectability of lesser disfiguration.

Hepatic rhabdomyosarcoma in an adult: a rare primary malignant liver tumor. Case report and literature review.

Rhabdomyosarcomas are malignant tumors that display features of striated muscle differentiation. They are the most common soft-tissue sarcomas among children and young adults. In mature adults however there are very rare. The liver as a primary site in adults has only been described in 12 cases. We report a case of a primary alveolar rhabdomyosarcoma of the liver in a 59 year old female, confirmed by histological examination using immunohistochemical analysis (positive actin, desmin, vimentin and myogenin staining) and fluorescent in situ hybridization (FISH) analysis (positivity for PAX3/FOXO1A fusion). The patient underwent primary surgical resection, but presented a few weeks after surgery already with recurrent disease in the abdomen and bone metastasis. Despite initial good response to chemotherapy (doxorubicin/ifosfamide) and stable disease at 12 months after diagnosis, the patient died 31 months after the first presentation secondary to complicated abundant abdominal recurrent disease. We further present a review of the literature on published similar cases since 1979.

[Atypical lipomatous tumors of the stomach. Clinical, morphological and molecular findings]. / Atypische lipomatöse Tumoren des Magens. Klinische, morphologische und molekularbiologische Befunde.

Two cases of primary gastric atypical lipomatous tumors (ALT) are presented. In case No.1, a 7x4x3 cm submucosal ALT (lipoma-like subtype) of the antrum/pyloric region in a 60-year-old woman was completely resected. Using interphase dual-color-FISH, MDM2- and CDK4 amplifications could be detected in distinguished amplicons. The patient was continuously free of disease after 56 months. In case No. 2, a 3.5 cm (in diameter) submucosal ALT (lipoma-like subtype) of the gastric body in a 56-year-old woman was completely resected. FISH revealed MDM2 amplification while the CDK4 gene remained in diploid copies. This patient was continuously free of disease after 36 months. The morphologic and molecular biological findings of this rare primary gastric mesenchymal tumor are discussed in comparison with the corresponding soft tissue lesions.

[Gardner fibroma: case report and discussion of a new soft tissue tumor entity]. / Gardner-Fibrom: Eine neue mesenchymale Tumorentität als Indikatorläsion.

Gardner fibroma represents a rare and recently described soft tissue tumor entity in children and young adults. It consists of haphazardly arranged coarse and hyalinized collagen fibers combined with loosely arranged bland spindle and fibroblastic cells. The case of a 13-year-old male patient with Gardner fibroma and osteoma and multicentric desmoid type fibromatosis in his mother is presented with detection of a (heterozygotic) germline mutation of the APC gene leading to a de novo stop codon (deletion of base pairs 5033-5036). FISH analysis revealed a structural loss of heterozygosity (LOH) in the APC gene on chromosomal locus 5q21 in one out of five analysed desmoids of the mother, no LOH of APC gene in the Gardner fibroma. Gardner fibroma in children and young adults may serve as an indicator lesion for familial adenomatous polyposis (FAP), Gardner syndrome, a familial desmoid type fibromatosis without other manifestations of APC or a new APC gene mutation. For the clinician, this diagnosis should be commented upon accordingly by the surgical pathologist. As the result of a detected APC gene mutation, continuous follow-up for the development of colorectal tumors and desmoid type fibromatosis as well as a familial screening for FAP is recommended.

[Lipoma and atypical lipomatous tumor within the same neoplasia: Evidence for a continuous transition]. / Lipom und atypischer lipomatöser Tumor innerhalb einer Neoplasie: Hinweis für einen kontinuierlichen Ubergang.

The case of a lipomatous tumor with a predominant lipoma component and transition to an atypical lipomatous tumor is presented. A deep-seated soft tissue tumor of the right thigh with a maximum size of 14 cm was resected in a 70-year-old female patient. Corresponding to a comparable macroscopic aspect, the lesion revealed the histological features of an ordinary lipoma without atypia in about 80% of the specimen. In the remaining portion (approximately 20%) histopathology showed an atypical lipomatous tumor (ALT, lipoma-like subtype). Immunohistochemistry for MDM 2 and CDK4 revealed no immunoreactivity in the lipoma component, but within the ALT component. Interphase dual-color fluorescence in situ hybridization showed no amplification of the MDM 2 gene and rarely CDK4 gene amplification within the lipoma component, but high level amplification of MDM 2/CDK4 gene in the ALT area, further supporting the morphologically based diagnosis of a lipomatous tumor including areas of a true lipoma and ALT. This case underlines the concept of a continuous stepwise development of lipomatous soft tissue tumors from benign to malignant counterparts as a biological continuum.

Complex tumor-specific t(X;18) in seven synovial sarcoma tumors.

Cytogenetic analysis was performed of six monophasic synovial sarcomas (four primary, two recurrent tumors) and one recurrent poorly differentiated synovial sarcoma with complex tumor-specific t(X;18). In the complex translocations, besides chromosomes X and 18, the following chromosomes were involved: 1, 3, 5, 15, and 17. In all, taking these results together with findings of 20 previously published synovial sarcoma tumors with complex t(X;18), 13 different chromosomes were involved. Chromosomes 15 (22% of tumors) and 1, 5, and 12 (approximately 11% each) were the most frequently involved in complex translocation, but with different breakpoints. In our laboratories, complex tumor-specific t(X;18) ranged from 2.5% to 11.7% (average 6.5%) of synovial sarcoma karyotypes.

Surgical resection of residual disease in initially inoperable imatinib-resistant/intolerant gastrointestinal stromal tumor treated with sunitinib.

AIM: Sunitinib malate therapy in inoperable and/or metastatic gastrointestinal stromal tumor (GIST) resistant to imatinib mesylate may facilitate surgical removal of residual disease. We explored this possibility in the course of treating patients as part of a treatment-use trial, the objective of which was to provide access to sunitinib treatment. METHODS: Four patients with inoperable and/or metastatic GIST resistant to imatinib who had responded to sunitinib therapy administered at a starting dose of 50 mg daily in 6-week cycles of 4 weeks on treatment followed by 2 weeks off underwent surgical removal of residual disease. Disease progression on or clinical response to treatment was defined based on Response Evaluation Criteria in Solid Tumors. RESULTS: In three of four cases it was possible to perform macroscopically complete resection of residual disease, resulting in surgical complete clinical responses, two with durations of 13 months. The fourth patient achieved a dramatic partial response to sunitinib that required emergency surgical resection of the necrotic tumor mass, with the partial response having been maintained for 15 months. In all cases, viable GIST cells were detected histologically in the resection specimens, and sunitinib treatment was resumed post-surgery. None of the patients experienced any postoperative complications during 13-16 months of follow-up. CONCLUSIONS: Combining sunitinib treatment with surgical removal of residual disease may allow selected imatinib-resistant GIST patients who have shown a favorable response to sunitinib to achieve complete and sustained remission or durable control of previously progressive disease beyond that expected for sunitinib treatment alone.

Relationship of imatinib-free plasma levels and target genotype with efficacy and tolerability.

Imatinib has revolutionised the treatment of chronic myeloid leukaemia (CML) and gastrointestinal stromal tumours (GIST). Using a nonlinear mixed effects population model, individual estimates of pharmacokinetic parameters were derived and used to estimate imatinib exposure (area under the curve, AUC) in 58 patients. Plasma-free concentration was deduced from a model incorporating plasma levels of alpha(1)-acid glycoprotein. Associations between AUC (or clearance) and response or incidence of side effects were explored by logistic regression analysis. Influence of KIT genotype was also assessed in GIST patients. Both total (in GIST) and free drug exposure (in CML and GIST) correlated with the occurrence and number of side effects (e.g. odds ratio 2.7+/-0.6 for a two-fold free AUC increase in GIST; P<0.001). Higher free AUC also predicted a higher probability of therapeutic response in GIST (odds ratio 2.6+/-1.1; P=0.026) when taking into account tumour KIT genotype (strongest association in patients harbouring exon 9 mutation or wild-type KIT, known to decrease tumour sensitivity towards imatinib). In CML, no straightforward concentration-response relationships were obtained. Our findings represent additional arguments to further evaluate the usefulness of individualizing imatinib prescription based on a therapeutic drug monitoring programme, possibly associated with target genotype profiling of patients.