Imatinib mesylate in advanced dermatofibrosarcoma protuberans: pooled analysis of two phase II clinical trials.

PURPOSE: Dermatofibrosarcoma protuberans (DFSP) is a dermal sarcoma typically carrying a translocation between chromosomes 17 and 22 that generates functional platelet-derived growth factor B (PDGFB). PATIENTS AND METHODS: Two distinct phase II trials of imatinib (400 to 800 mg daily) in patients with locally advanced or metastatic DFSP were conducted and closed prematurely, one in Europe (European Organisation for Research and Treatment of Cancer [EORTC]) with 14-week progression-free rate as the primary end point and the other in North America (Southwest Oncology Group [SWOG]) with confirmed objective response rate as the primary end point. In the EORTC trial, confirmation of PDGFB rearrangement was required, and surgery was undertaken after 14 weeks if feasible. The SWOG study confirmed t(17;22) after enrollment. RESULTS: Sixteen and eight patients were enrolled onto the EORTC and SWOG trials, respectively. Tumor size ranged from 1.2 to 49 cm. DFSP was located on head/neck, trunk, and limb in seven, 11, and six patients, respectively, and was classic, pigmented, and fibrosarcomatous DFSP in 13, one, and nine patients, respectively. Metastases were present in seven patients (lung involvement was present six patients). Eleven patients (4%) had partial response as best response, and four patients had progressive disease as best response. Median time to progression (TTP) was 1.7 years. Imatinib was stopped in 11 patients because of progression, one patient because of toxicity, and two patients after complete resection of disease. Median overall survival (OS) time has not been reached; 1-year OS rate was 87.5%. CONCLUSION: Imatinib is active in DFSP harboring t(17;22) including fibrosarcomatous DFSP, with objective response rate approaching 50%. Response rates and TTP did not differ between patients taking 400 mg daily versus 400 mg twice a day.

Phase II study of plitidepsin 3-hour infusion every 2 weeks in patients with unresectable advanced medullary thyroid carcinoma.

OBJECTIVES: To evaluate the antitumor response, time-to-event efficacy endpoints and toxicity of plitidepsin (Aplidin) 5 mg/m as a 3-hour intravenous (i.v.) infusion every 2 weeks in patients with unresectable advanced medullary thyroid carcinoma (MTC). METHODS: Sixteen patients with MTC and disease progression or large tumor burden received plitidepsin. Tumor response and time-related parameters were evaluated according to Response Evaluation Criteria in Solid Tumors. Secondary efficacy endpoints were marker response (calcitonin and carcinoembryonic antigen), clinical benefit and quality of life. Safety was assessed using the National Cancer Institute Common Toxicity Criteria. RESULTS: A total of 141 cycles (median, 9 per patient; range, 1-24) were administered. No complete responses or partial responses (PR) were found, and 12 patients had stable disease for >8 weeks. Median follow-up was 15.0 months. Median time to progression was 5.3 months. Median overall survival could not be calculated, but 86.7% and 66.0% of patients were alive at 6 and 12 months. Marker response included 1 unconfirmed PR and 2 stabilizations for calcitonin, and 1 unconfirmed PR and 4 stabilizations for calcitonin and carcinoembryonic antigen. One patient showed clinical benefit. Quality of life scores generally decreased during the study. Most treatment-related adverse events were mild or moderate. Grade 3 lymphopenia was the only severe hematological toxicity found (2 patients). Severe nonhematological toxicities were grade 3 creatine phosphokinase increase (2 patients, with no myalgia or muscular weakness) and transient grade 3 alanine aminotransferase increase (5 patients). CONCLUSIONS: Single-agent plitidepsin given as 3-hour i.v. infusions every 2 weeks was generally well tolerated but showed limited clinical activity in patients with unresectable advanced MTC.

Clinical impact of trabectedin (ecteinascidin-743) in advanced/metastatic soft tissue sarcoma.

BACKGROUND: Patients with advanced or metastatic non-gastrointestinal stromal tumour soft tissue sarcoma (STS) whose disease progresses during or after chemotherapy with doxorubicin or ifosfamide have few options and very limited life expectancy. In this setting, the DNA and transcription interacting agent trabectedin (ecteinascidin-743), isolated originally from the tunicate Ecteinascidia turbinata, has encouraging activity and is now approved in the European Union. OBJECTIVE: To review evidence for the efficacy of trabectedin in STSs. METHODS: This review includes material known to the authors through preclinical and clinical work with trabectedin, and information from relevant papers and abstracts. RESULTS: Pooled analysis of Phase II studies suggests that around 50% of STS patients, failing conventional chemotherapy, experienced long lasting tumour control (either objective response or stabilization of disease) when treated with trabectedin. Twenty-nine per cent of patients were alive at 2 years, and median overall survival was 10.3 months. Leiomyosarcomas and liposarcomas appear particularly sensitive to the drug. In myxoid and round-cell liposarcomas trabectedin seems exceptionally active. A link between specific translocations underlying this disease and the drug's mechanism of action is being explored. Trabectedin is also active in synovial, ewing sarcoma and other translocation-related STSs. Trabectedin is not cardio- or neurotoxic. The neutropenia and hepatic toxicity that occur are non-cumulative, reversible, and lessened by steroid premedication. The lack of cumulative toxicities could make trabectedin appropriate for prolonged treatment. CONCLUSION: The potential of trabectedin should be further explored in STSs in general and in specific subtypes, both in combination with other cytotoxic agents and with modulators of intracellular signalling.

A phase II trial of docetaxel (Taxotere) as second-line chemotherapy in patients with metastatic breast cancer.

The efficacy and tolerability of docetaxel 100 mg/m(2) every 3 weeks as second-line chemotherapy in patients with metastatic breast cancer was investigated. In addition, the efficacy of a 3-day prophylaxis against cumulative dose-related fluid retention was examined with methylprednisolone 32 mg twice daily for 3 days starting 12 and 3 h before the docetaxel infusion together with oral cetirizine 10 mg 12 and 3 h before start of docetaxel for prevention of acute hypersensitivity reactions. According to the intent to treat-analysis 35% (95%CI: 25; 46) of the 94 patients entered responded to therapy. Their median survival was 12 months (range 0-20 months). The respective response rate for the 87 patients eligible for response evaluation was 37% (95%CI: 27; 48). Their median duration of response was 8 months (range 3-12 months), their median time to progression was 4 months (range 1-12 months). The corresponding response rate in the eligible patient cohort with anthracycline-resistant disease was 28% (95%CI: 15; 45) and increased to 44% (95%CI: 30; 59) in the cohort with non-anthracycline-resistant disease. Patients with visceral metastases responded in 36% and patients with > or = 3 organs involved in 33%. In a retrospective analysis, the 3-day premedication of corticosteroids and antihistamines proved to be as effective as the established but more toxic 5-day regimen in delaying and preventing the occurrence of docetaxel derived toxicities especially the cumulative fluid retention. In conclusion, docetaxel represents one of the most active agents for second-line treatment of metastatic breast cancer, especially for anthracycline-resistant patients. Due to comparable effectiveness of the 5-day regimen which is widely used by others and the 3-day premedication tested in this trial the latter proved to be more favourable and was therefore recommended for future therapies.

Intra-hepatic Mitomycin C bolus infusion in the treatment of extensive liver metastases of breast cancer.

BACKGROUND: In the treatment of extensive liver metastasis of breast cancer (LMBC), locally administered Mitomycin C (MMC) to the liver might be an effective approach with limited toxicity. PATIENTS AND METHODS: We retrospectively reviewed the records of 30 patients with LMBC treated with intra-hepatic MMC at our institution. MMC (12 mg) was administered by transcatheter bolus infusion into the hepatic arteries every 4 weeks. Tumour response according to RECIST criteria, progression free survival (PFS), overall survival (OS) and duration of response (DR) were used to evaluate efficacy. RESULTS: There was a local response in the liver and a global response in respectively 33 and 26%. The median PFS, DR and OS were 3, 4 and 7 months, respectively. There was more benefit in patients without documented metastases outside the liver and without severe liver dysfunction. Thrombocytopenia, leucocytopenia and an allergic reaction were observed after MMC administration in 20 (67%), 12 (40%) and 4 patients (13%), respectively. CONCLUSION: Intra-hepatic MMC bolus infusion as treatment of extensive LMBC is associated with limited toxicity and has a significant response rate in the liver. Prospective investigations are required to define the place of this modality for treating patients with breast cancer liver metastases.

Imatinib does not induce cardiac left ventricular failure in gastrointestinal stromal tumours patients: analysis of EORTC-ISG-AGITG study 62005.

Recent publications have suggested that imatinib (Glivec) may be cardiotoxic. We have therefore assessed the largest study on the agent performed in patients with gastrointestinal stromal tumours, randomising a daily dose of 400mg versus 800 mg. 946 Patients were entered, 942 patients received at least one dose of imatinib. The median time on treatment was 24 months. A total of 24,574 exposure months could be analysed. We could not identify an excess of cardiac events in the study population. In 2 patients (0.2%) a possible cardiotoxic effect of imatinib could not fully be excluded. The current analysis of a large randomised prospective study could not confirm previous suggestions of imatinib induced cardiac toxicity.

A phase I and pharmacokinetic study of LAF389 administered to patients with advanced cancer.

LAF389 is a synthetic analogue of bengamide B, a natural product isolated from Jaspidae sponges. LAF389 has both antiproliferative and antiangiogenetic properties, and preclinical investigations showed a broad antitumour activity. This clinical trial aimed to determine the safety and pharmacokinetic profile of LAF389 administered as a slow intravenous injection for 3 consecutive days every 3 weeks in patients with advanced solid tumours. Eight dose levels were tested: 1, 2.5, 5, 10, 15, 30, 25 and 20 mg/day. A total of 33 patients, median age 52 years (range 33-72), with refractory solid tumours were enroled, 19 men and 14 women with a median World Health Organization performance status of 1 (0-4). Seventy-eight cycles of treatment have been administered (mean 2.5, range 1-10). Four cardiovascular dose-limiting toxicities were reported at 30 mg (2/2 patients) and 25 mg (2/9 patients), eight additional patients at various dose levels had (cardio)vascular toxicity, probably drug related, and one patient died owing to pulmonary embolism at the 5 mg dose. No objective responses were recorded. Pharmacokinetic parameters were variable, although linear and without obvious accumulation from cycle I to cycle II. LAF389 dose escalation was terminated owing to occurrence of unpredictable cardiovascular events. This, associated with the lack of clinical activity, did not warrant further investigation of this agent.

Docetaxel and gemcitabine combination therapy in advanced transitional cell carcinoma of the urothelium: results of a phase II and pharmacologic study.

Our objective was to determine the response to gemcitabine plus docetaxel in advanced urothelial transitional cell carcinoma in a phase II trial, and gemcitabine distribution between plasma and erythrocytes, following docetaxel administration. Patients with locally advanced or metastatic transitional cell carcinoma, following a maximum of one prior chemotherapy regimen, were given gemcitabine 800 mg/m on days 1 and 8 plus docetaxel 85 mg/m on day 8, every 21 days. Gemcitabine was measured in the plasma and erythrocytes of nine patients before and after docetaxel administration. Thirty-four patients (median 63 years; range 49-79 years), of whom seven had prior chemotherapy and 27 were chemotherapy-naive, received a median of six cycles (range 1-6). Complete and partial remissions were observed in two and 16 (including three pretreated) patients, respectively, for an overall response rate of 53%. Median response duration was 5 months (range 1-39+). Haematoxicity was manageable, despite grade 3 infections in 24% of patients, but other toxicities were mostly mild. An apparent shift of gemcitabine from plasma to erythrocytes occurred after docetaxel in five of six patients evaluable for this analysis. We conclude gemcitabine plus docetaxel is tolerable and highly active in treated and untreated patients with advanced transitional cell carcinoma.

Efficacy and safety of sunitinib in patients with advanced gastrointestinal stromal tumour after failure of imatinib: a randomised controlled trial.

BACKGROUND: No effective therapeutic options for patients with unresectable imatinib-resistant gastrointestinal stromal tumour are available. We did a randomised, double-blind, placebo-controlled, multicentre, international trial to assess tolerability and anticancer efficacy of sunitinib, a multitargeted tyrosine kinase inhibitor, in patients with advanced gastrointestinal stromal tumour who were resistant to or intolerant of previous treatment with imatinib. METHODS: Blinded sunitinib or placebo was given orally once daily at a 50-mg starting dose in 6-week cycles with 4 weeks on and 2 weeks off treatment. The primary endpoint was time to tumour progression. Intention-to-treat, modified intention-to-treat, and per-protocol analyses were done. This study is registered at ClinicalTrials.gov, number NCT00075218. FINDINGS: 312 patients were randomised in a 2:1 ratio to receive sunitinib (n=207) or placebo (n=105); the trial was unblinded early when a planned interim analysis showed significantly longer time to tumour progression with sunitinib. Median time to tumour progression was 27.3 weeks (95% CI 16.0-32.1) in patients receiving sunitinib and 6.4 weeks (4.4-10.0) in those on placebo (hazard ratio 0.33; p<0.0001). Therapy was reasonably well tolerated; the most common treatment-related adverse events were fatigue, diarrhoea, skin discolouration, and nausea. INTERPRETATION: We noted significant clinical benefit, including disease control and superior survival, with sunitinib compared with placebo in patients with advanced gastrointestinal stromal tumour after failure and discontinuation of imatinab. Tolerability was acceptable.

Predicting toxicities for patients with advanced gastrointestinal stromal tumours treated with imatinib: a study of the European Organisation for Research and Treatment of Cancer, the Italian Sarcoma Group, and the Australasian Gastro-Intestinal Trials Group (EORTC-ISG-AGITG).

The aim of this study was to identify prognostic factors for toxicity to treatment with imatinib. The study was based on 942 patients with gastrointestinal stromal tumours (GIST) randomised to receive imatinib at different doses. The correlation between toxicities occurring with a Common Toxicity Criteria (CTC) grade 2 or more (non-haematological) or grade 3 or 4 (haematological) and imatinib dose, age, sex, performance status, original disease site, site and size of lesions at trial entry, baseline haematological and biological parameters was investigated. Anaemia was correlated with dose and baseline haemoglobin level, and neutropaenia with baseline neutrophil count and haemoglobin level. The risk of non-haematological toxicities was dose dependent and higher in females (oedema, nausea, diarrhoea), and in patients of advanced age (oedema, rash fatigue), poor performance status (fatigue and nausea), prior chemotherapy (fatigue), tumour of identified gastrointestinal origin (diarrhoea) and small lesions (rash). A multivariate risk calculator that can be used in the clinic for individual patients is proposed.

Association of enzyme and transporter genotypes with the pharmacokinetics of imatinib.

OBJECTIVE: Our objective was to explore the relationships between imatinib pharmacokinetics and 9 allelic variants in 7 genes coding for adenosine triphosphate-binding cassette transporters (ABCB1 and ABCG2) and enzymes (cytochrome P450 [CYP] 2C9, CYP2C19, CYP2D6, CYP3A4, and CYP3A5) of putative relevance for imatinib. METHODS: Imatinib transport in vitro was studied by use of human embryonic kidney 293 cells transfected with wild-type ABCG2 and an ABCG2 Q141K clone. Steady-state pharmacokinetics of imatinib was obtained in 82 patients with gastrointestinal stromal tumors treated with oral imatinib at doses ranging from 100 to 1000 mg/d. Genotyping was carried out via direct sequencing or restriction fragment length polymorphism-based techniques. RESULTS: Human embryonic kidney 293 cells transfected with ABCG2 Q141K exhibited greater drug accumulation in vitro in comparison with cells expressing wild-type ABCG2 (P = .028). However, pharmacokinetic parameters of imatinib in vivo were not statistically significantly different in 16 patients who were heterozygous for ABCG2 421C>A compared with 66 patients carrying the wild-type sequence (P = .479). The apparent oral clearance of imatinib was potentially reduced in individuals with at least 1 CYP2D6*4 allele (median, 7.78 versus 10.6 L/h; P = .0695). Pharmacokinetic parameters were not related to any of the other multiple-variant genotypes (P >or= .230), possibly because of the low allele frequencies. CONCLUSIONS: This study indicates that common genetic variants in the evaluated genes have only a limited impact on the pharmacokinetics of imatinib. Further investigation is required to quantitatively assess the clinical significance of homozygous variant ABCG2 and CYP2D6 genotypes in patients treated with imatinib.

Everolimus alters imatinib blood partition in favour of the erythrocyte.

The signal transduction inhibitor imatinib is one of the latest breakthroughs in cancer pharmacotherapy. It is administered orally over prolonged periods of time for the treatment of gastro-intestinal stromal tumours. Routine therapeutic drug monitoring of blood plasma versus red blood cells over several years by liquid chromatography coupled tandem mass spectrometry has high-lighted a very intriguing phenomenon. Imatinib plasma availability decreases dramatically owing to a significant shift in the partition ratio of red blood cells versus plasma. The shift is enforced by combination with everolimus, another signal transduction inhibitor. These data warrant routine erythrocyte versus plasma monitoring to prevent unexpected alterations in drug efficacy during long-term treatment.

KIT mutations and dose selection for imatinib in patients with advanced gastrointestinal stromal tumours.

A recent randomized EORTC phase III trial, comparing two doses of imatinib in patients with advanced gastrointestinal stromal tumours (GISTs), reported dose dependency for progression-free survival. The current analysis of that study aimed to assess if tumour mutational status correlates with clinical response to imatinib. Pre-treatment samples of GISTs from 377 patients enrolled in phase III study were analyzed for mutations of KIT or PDGFRA by combination of D-HPLC and direct sequencing of tumour genomic DNA. Mutation types were correlated with patients' survival data. The presence of exon 9-activating mutations in KIT was the strongest adverse prognostic factor for response to imatinib, increasing the relative risk of progression by 171% (P<0.0001) and the relative risk of death by 190% (P<0.0001) when compared with KIT exon 11 mutants. Similarly, the relative risk of progression was increased by 108% (P<0.0001) and the relative risk of death by 76% (P=0.028) in patients without detectable KIT or PDGFRA mutations. In patients whose tumours expressed an exon 9 KIT oncoprotein, treatment with the high-dose regimen resulted in a significantly superior progression-free survival (P=0.0013), with a reduction of the relative risk of 61%. We conclude that tumour genotype is of major prognostic significance for progression-free survival and overall survival in patients treated with imatinib for advanced GISTs. Our findings suggest the need for differential treatment of patients with GISTs, with KIT exon 9 mutant patients benefiting the most from the 800 mg daily dose of the drug.

Cellular uptake of the tyrosine kinase inhibitors imatinib and AMN107 in gastrointestinal stromal tumor cell lines.

Imatinib and AMN107 are protein tyrosine kinase inhibitors which reduce KIT autophosphorylation with similar potency. This report describes the cellular uptake of these compounds in two human gastrointestinal stromal tumor (GIST)-derived cell lines (GIST882 and GIST GDG1), which both express constitutively activated KIT. In GIST882 and GIST GDG1 cell lines, HPLC analysis revealed AMN107 intracellular concentrations to be 7- and 10-fold greater than those of imatinib. These data indicate either increased cellular uptake or decreased cellular efflux of AMN107 when compared to imatinib in GIST cell lines. The finding suggests that AMN107 might be less susceptible to transport-driven imatinib resistance. The stable and increased exposure of GIST cells to a highly active AMN107 agent could be important in the treatment of imatinib-resistant GIST patients in whom resistance has developed as a result of changes in cellular transport mechanisms for which AMN107 is not a substrate.

Clinical and molecular studies of the effect of imatinib on advanced aggressive fibromatosis (desmoid tumor).

PURPOSE: To determine the clinical efficacy of imatinib in patients with advanced aggressive fibromatosis (AF) and to identify the molecular basis of response/nonresponse to this agent. PATIENTS AND METHODS: Nineteen patients with AF were treated with imatinib (800 mg/d) as part of a phase II clinical study. Tumor specimens were analyzed for mutations of KIT, PDGFRA, PDGFRB, and CTNNB1 (beta-catenin). Tumor expression of total and activated KIT, PDGFRA, and PDGFRB were assessed using immunohistochemistry and immunoblotting techniques. We also measured plasma levels of PDGF-AA and PDGF-BB in patients and normal patient controls. RESULTS: Three of 19 patients (15.7%) had a partial response to treatment, with four additional patients having stable disease that lasted more than 1 year (overall 1 year tumor control rate of 36.8%). No mutations of KIT, PDGFRA, or PDGFRB were found. Sixteen of 19 patients (84%) had mutations involving the WNT pathway (APC or CTNNB1). However, there was no correlation between WNT pathway mutations and clinical response to imatinib. AF tumors expressed minimal to null levels of KIT and PDGFRA but expressed levels of PDGFRB that are comparable with normal fibroblasts. However, PDGFRB phosphorylation was not detected, suggesting that PDGFRB is only weakly activated. AF patients had elevated levels of PDGF-AA and PDGF-BB compared with normal patient controls. Notably, the plasma level of PDGF-BB was inversely correlated with time to treatment failure. CONCLUSION: Imatinib is an active agent in the treatment of advanced AF. Imatinib response in AF patients may be mediated by inhibition of PDGFRB kinase activity.

Imatinib (Gleevec, Glivec) tumour tissue analysis by measurement of sediment and by liquid chromatography tandem mass spectrometry.

The analysis of the signal transduction inhibitor imatinib in patient tumour tissue using LC and MS/MS is described. The anticancer agent is eluted over RP-C18 within 2 mm together with its internal standard STI571-d8. Calibration curves were prepared in red blood cells (RBC). For quantitative isolation of the RBC, measurement of sediment was applied. There were no indications of signal suppression by substances originating in the biological matrix. The limit of determination in tumour tissue was in the range of those recorded for RBC and plasma. The assay is selective and sensitive, with its robustness favouring the experimental application in clinical oncology and its routine use in animal experiments. The LOD was 4.5 ng per gram in tumour tissue.

Proteomics in cancer research: methods and application of array-based protein profiling technologies.

With the human genome sequence now determined, the field of molecular medicine is moving beyond genomics to proteomics, the large-scale analysis of proteins. It is now possible to examine the expression of more than 1000 proteins using mass spectrometry technology coupled with various separation methods. Microarray technology is a new and efficient approach, for extracting relevant biomedical data and has a wide range of applications. It provides a versatile tool to study protein-protein, protein-nucleic acid, protein-lipid, enzyme-substrate and protein-drug interactions. This review paper will explore the key themes in proteomics and their application in clinical cancer research.

Imatinib for the treatment of patients with unresectable or metastatic malignant KIT-positive gastrointestinal stromal tumours: an open-label Belgian trial.

BACKGROUND: Gastrointestinal stromal tumours (GIST) are the most common mesenchymal tumours of the gastrointestinal tract. They are defined immunohistologically as KIT positive tumours. The only effective treatment for malignant GIST was surgery until 2000. Imatinib mesylate (STI571, Glivec) has shown substantial anticancer activity in patients with metastatic or unresectable GIST. PATIENTS AND METHODS: 57 patients who were diagnosed with unresectable or metastatic malignant GIST were entered into this study. The patients were given 400 mg Glivec orally once daily. The dose could be increased to 600 mg orally once daily and then to 400 mg twice daily if tumour progression was noticed. Daily treatment was interrupted or dose was decreased only in the case of limiting toxicities. We evaluated the tumour response and the safety of the drug. RESULTS: 85% of GIST patients showed a partial response or stable disease after 8 weeks of treatment with imatinib. The main side effects were nausea, vomiting, anorexia, skin rash, periorbital oedema and diarrhea. CONCLUSION: This study confirms that imatinib is an active agent against malignant GIST with manageable toxicities.

Phase I and pharmacologic study of PKI166, an epidermal growth factor receptor tyrosine kinase inhibitor, in patients with advanced solid malignancies.

PURPOSE: This phase I study was conducted to assess the tolerability, pharmacokinetics, and antitumor activity of the oral, selective epidermal growth factor receptor tyrosine kinase inhibitor PKI166 in patients with advanced solid malignancies. EXPERIMENTAL DESIGN: PKI166 was first given once daily continuously and in the second part of the study once daily for 2 weeks every 4 weeks to establish the maximum tolerated dose (MTD). Ten additional patients were studied at MTD to acquire additional safety information and characterize the effect of food intake on PKI166 pharmacokinetics. Pharmacokinetics of PKI166 were characterized after single and multiple doses at all dose levels. RESULTS: Fifty-four patients received a total of one hundred sixteen 28-day cycles of PKI166. Dose-limiting transaminase elevations were observed in two of seven and two of eight patients using 50 and 100 mg PKI166 continuously. In the second part with PKI166 once daily for 2 weeks every 4 weeks, MTD was set at 750 mg. Dose-limiting toxicity consisted of diarrhea, skin rash, and transaminase elevations. Pharmacokinetic analysis revealed fast absorption, a linear dose-response relationship without drug accumulation after multiple doses. At MTD, no significant influence of food intake on PKI166 pharmacokinetics was observed. Stable disease for more than two cycles was observed in 11 patients. CONCLUSIONS: PKI166 given once daily for 2 weeks every 4 weeks is well tolerated with linear pharmacokinetics, compatible with once daily dosing, and without significant effect of food intake on absorption. The recommended dose for further studies is 750 mg once daily for 2 weeks every 4 weeks.

Initial and late resistance to imatinib in advanced gastrointestinal stromal tumors are predicted by different prognostic factors: a European Organisation for Research and Treatment of Cancer-Italian Sarcoma Group-Australasian Gastrointestinal Trials Group study.

PURPOSE: The aim of this study was to identify factors predicting initial and late resistance of GI stromal tumor (GIST) patients to imatinib and to document the dose-response relationship in the prognostic subgroups. This study is based on the European Organisation for Research and Treatment of Cancer-Italian Sarcoma Group-Australasian Gastrointestinal Trials Group randomized trial comparing two doses of imatinib in advanced disease. PATIENTS AND METHODS: Initial resistance was defined as progression within 3 months of randomization, and late resistance was defined as progression beyond 3 months. Investigated cofactors include imatinib dose, age, sex, performance status, original disease site, site and size of lesions at trial entry, and baseline hematologic and biologic parameters. RESULTS: Initial resistance was recorded for 116 (12%) of 934 assessable patients and was independently predicted by the presence of lung and absence of liver metastases, low hemoglobin level, and high granulocyte count. Among 818 patients who were alive and progression free at 3 months, 347 subsequent progressions were recorded, and late resistance was independently predicted by high baseline granulocyte count, primary tumor outside of the stomach, large tumor size, and low initial imatinib dose. The impact of initial dose on late resistance was mainly significant in patients with a high baseline granulocyte count (> 5.10(9)/L) and in patients with tumors of GI origin outside of the stomach and small intestine. CONCLUSION: Our study identifies patients for whom initial and/or long-term treatment needs to be improved and patients who require a high initial dose. Correlation of these results with immunohistochemistry and molecular parameters may further help to understand the biologic mechanisms of resistance.