Real world treatment patterns of gastrointestinal stromal tumor patients

e15602

Background: Imatinib is accepted as the standard first-line therapy to treat gastrointestinal stromal tumor (GIST) in patients with unresectable or metastatic disease. In the case of disease progression, physicians may consider increasing imatinib dose or switching to another second-line agent, such as sunitinib. The aim of this study was to analyze the real-world long term treatment patterns of GIST patients. Methods: Two large claims databases from 01/1999 to 03/2008 were combined (MarketScan and Ingenix Impact) to extract patients diagnosed with GIST who initiated on imatinib ≥400 mg/day. Patients were followed from the first observed imatinib prescription to the end of data availability. Patients who dose increased during the study period were defined as dose escalators, while patients who later switched to sunitinib with or without dose escalation were defined as switchers. Kaplan Meier analyses were used to estimate the rate of treatment changes over time including imatinib discontinuation, defined as a lack of imatinib supply for ≥60 days, and switching back to initial treatment. Results: Among the 1,508 GIST patients who initiated on imatinib, 253 patients had a dose increase and 153 patients switched to sunitinib during the study period. 20.1% patients on imatinib discontinued by the end of the first year, and 43.0% discontinued by the end of the third year. Among the 153 switchers, 61 patients had a dose escalation prior to the switch, of which 82.0% reached 800 mg before switching. Among all the switchers, 20.3% switched back to imatinib within 6 months. Conclusions: These claims-based findings on the duration of first-line imatinib therapy of GIST patients supports data on imatinib efficacy in treating GIST from formal clinical research studies. Most of GIST patients who initiated imatinib continued on this therapy without undergoing dose increase or switch to sunitinib. Among switchers, most did not dose escalate before switching and many eventually switched back to imatinib. It appears that physicians tend to not always follow clinical practice guidelines developed based on expert consensus, with respect to decision rules for dose escalation, or for the appropriate time to change kinase inhibitor therapy.

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Adverse events associated with escalating imatinib versus switching to dasatinib in patients with chronic myelegenous leukemia

7092

Background: After initial therapy with imatinib, some chronic myelegenous leukemia (CML) patients may require dose escalation or switching to another BCR/ABL kinase inhibitor to achieve the desired response. This study compared adverse events associated with either escalation of imatinib or switching to dasatinib. Methods: Two large administrative claims databases were combined (MarketScan and Ingenix Impact) to extract deidentified information on 17,382 patients diagnosed with CML (ICD-9 code: 205.1) from January 1999 to March 2008. 474 patients (dose escalators) had their dose of imatinib increased at some point to >400 mg/day but were never given dasatinib, while 175 patients were switched to dasatinib with or without dose escalation of imatinib (switchers). Patients were followed from the index date to treatment discontinuation or end of eligibility. Cox proportional-hazard models were used to compare the risk of common adverse events (AEs) associated with escalation or switching to dasatinib, controlling for demographics, imatinib treatment patterns, and prior therapies at baseline. Patients with the studied AEs at baseline were excluded from analyses of the corresponding AEs. Results: Switchers experienced significantly higher risk of the following AEs than escalators: fluid retention (HR 3.22 p < 0.0001), pleural effusion (HR 4.90 p < 0.0001), thrombocytopenia (HR 3.25 p = 0.0044), neutropenia (HR 3.40 p = 0.0009), and some non-hematologic adverse events (HR 2.38 p < 0.0001), dyspnea (HR 4.02 p < 0.0001), constipation (HR 5.79 p = 0.0041), nausea and vomiting (HR 2.40 p = 0.0100), and congestive heart failure (HR 5.01 p < 0.0001). No statistically significant differences in risk of other common AEs associated with imatinib and dasatinib were identified. Conclusions: 15.4% of CML patients treated with ≤400mg of imatinib initially either had dose escalation or switch to dasatinib. Significantly more AEs were associated to those who switched to dasatinib than those who dose escalated. Further study is warranted to examine the causality of the difference in these AEs.

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Genetic evolution of EGFR and the clonal origin of adenocarcinomas exhibiting various degrees of bronchioloalveolar carcinoma

e22050

Background: EGFR mutations may accumulate during multistage progression of bronchioloalveolar carcinoma (BAC), leading to heterogeneity within the tumor. Moreover, intrapulmonary emersions are the predominant sites of BAC progression in the absence of other distant metastases. In cases of emerging bilateral lung lesions during the follow-up to complete resection, the issue of how to differentiate between lesions originating from multifocal BACs or distant metastases/local recurrence is an important and unresolved issue. This study was performed to determine whether sequential adenocarcinoma with BAC features emerges in the lung field arises from a single clone or multiple clones in the same individual. Methods: Samples of adenocarcinomas exhibiting various degrees of BAC were obtained by thoracotomy. Sequential specimens were obtained on detection of novel lesions in the lung field. Genomic DNA was extracted from the specimens, and the presence of activating mutations in EGFR was analyzed by direct sequencing. Our pathological findings, sequential imaging, and EGFR sequence data were compared to monitor evidence of cancer evolution. Results: Based on an analysis of EGFR in tumor specimens from 428 lung cancer patients, fifteen cases of sequential BAC-related adenocarcinoma obtained by thoracotomy were identified. Together with alterations in BAC/adenocarcinoma components, the EGFR-TKI untreated series with at least one episode of EGFR-activating mutations represented three typical models: no significant EGFR evolution for a single clone, genetic alterations from mutant to wild-type EGFR for multifocal lesions, and a switch from wild-type to mutant EGFR, which might exhibit uncertain circumstances of cancer progression. Conclusions: Genetic analysis in conjunction with pathological and radiological diagnoses can be used to explore the origin of multifocal BAC. The single clone model indicates subsequent disease progression, whereas genetic alterations from mutations to wild-type EGFR are suggestive of secondary primary carcinoma. When additional lesions emerge after radical resection of BAC-related lung cancer, sequential tumor samples should be obtained for further evaluation.

No significant financial relationships to disclose.

KRAS mutation in the primary or acquired resistance of Chinese NSCLC to EGFR tyrosine kinase inhibitors

e19071

Background: Prevalence of KRAS mutation in Asian NSCLC is different to population of white ethnicity. Data about KRAS mutation after development of resistance to EGFR tyrosine kinase inhibitors (TKIs) are rare. This study was to investigate the prevalence of KRAS mutation in Chinese NSCLC after primary or acquired resistance to EGFR TKIs. Methods: 155 EGFR TKI-naive NSCLC patients and corresponding tumor specimens were collected to establish baseline of KRAS mutation. 45 specimens from six patients with primary resistance to TKIs and twenty-nine patients with acquired resistance to TKIs were analyzed. Genomic DNA was prepared after purified cancer cells were isolated by laser microdissection. Mutations in codon 12 and 13 of the KRAS gene in TKI-naive patients were analyzed by direct sequencing. Mutations in TKI-resistant patients were meanwhile detected by DxS KRAS Mutation Test Kit and direct sequencing. Results: KRAS mutation (G12X) was detected in 7.1% (11/155) of the TKI- naive patients by direct sequencing. In 6 primary resistant patients (two paired specimens and four resistant specimens) and in 29 acquired resistant patients (eight paired specimens and twenty-one resistant specimens), absence of KRAS mutation was detected in all pre- treatment and post-treatment tissues by both methods. Conclusions: KRAS mutation exists in TKI-naive NSCLC patients instead of TKI-resistant setting. KRAS mutation couldn’t thoroughly explain the primary resistance to EGFR TKIs and it might not be the crucial consideration in the mechanisms of acquired resistance.

No significant financial relationships to disclose.

Treatment patterns of chronic myelogenous leukemia patients with suboptimal responses to imatinib

7090

Background: Imatinib is the first-line therapy for Philadelphia chromosome-positive chronic myelogenous leukemia (CML). Patients with suboptimal responses may have the dose of imatinib escalated or may be switched to an alternative kinase inhibitor such as dasatinib. The aim of this study is to examine the real-world treatment patterns of imatinib and dasatinib in CML patients. Methods: Two large U.S. administrative claims databases from January 1999 to March 2008 were combined (MarketScan and Ingenix Impact) to extract de-identified information of patients diagnosed with CML (ICD-9 code: 205.1) who were initiated on imatinib. Patients were followed from the first observed imatinib prescription to the end of data availability. Patients who increased imatinib dose to >400 mg/day were defined as dose escalators, while patients who initiated on imatinib and further switched to dasatinib were considered as switchers. Rates of imatinib dose escalation and switching to dasatinib were estimated. Kaplan-Meier (KM) survival analyses were used to estimate the rate of imatinib discontinuation, defined as a lack of imatinib supply for at least 90 days. Among switchers, the rate of switching back to imatinib was also estimated using KM survival analysis. Results: Among the 5,159 CML patients initiated with imatinib, 1,144 patients either had dose escalation of imatinib (839) or were switched to dasatinib (305) during the study period. Of the 5,159 patients, 12.1% patients discontinued imatinib by the end of the first year, and 25.4% discontinued by the end of the third year. Among the 305 switchers, 115 (37.7%) had an imatinib dose increase prior to the switch, and 66 (21.6%) were escalated to 800 mg of imatinib before switching. 51 patients (16.7%) had used imatinib for <6 months before switching, and 17.1% switched back to imatinib within 6 months of dasatinib treatment. Conclusions: This study showed that great variability was observed in the real world treatment pattern of CML patients. Most CML patients who initiated on imatinib did not dose increase or switch during the study period. Of those who switched to dasatinib, most did not attempt to increase the dose before switching, and a sizeable portion of patients had to switch back to imatinib.

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In vitro sequence-dependent interaction between paclitaxel and gefitinib in human lung cancer cell lines

e22025

Background: Cytotoxicity chemotherapy has been standard first line treatment for advanced NSCLC. Clinical trials comparing first line EGFR TKI therapy over cytotoxicity chemotherapy are under investigation in phase III trials. The aim of this study is to test the hypothesis that paclitaxel followed by gefitinib would be superior to the opposite order in EGFR TKI resistant cell lines because of cell signaling pathway and cell cycle interaction. Methods: we have used EGFR-TKI resistant human lung cancer cell lines A549, H1975 and H1650 as an in vitro model for defining the differential effects of opposite sequence of combination of cytotoxic drug and anti- EGFR agents on cell growth, signaling pathway, cell cycle distribution and induction of apoptosis. Results: Paclitaxel 24 hours followed by gefitinib 72 hours in A549, H1975 and H1650 cells produced synergistic effects, while the reverse sequence produced antagonistic effects. Exposure to paclitaxel resulted in an increased pEGFR and pAKT level, this increase of phosphorylation can be inhibited by the following gefitinib exposure, while the reverse sequence resulted in no change in EGFR and AKT phosphorylation. We confirmed that gefitinib arrested the cells in G1, paclitaxel arrested cells in S phase. The sequence of paclitaxel followed by gefitinib cause cells arrested in G1, while the reverse sequence cause cells arrested in S and G2 phase. Conclusions: These findings suggest that the sequence of paclitaxel followed by gefitinib may be superior to the reverse sequence in gefitinib resistant NSCLC, and support the investigation of these sequential treatment in the clinical setting. This work was supported by the grants from the National Natural Science Foundation of China (No. 30772531).

No significant financial relationships to disclose.

Circadian modulation of light-induced locomotion responses in Drosophila melanogaster

The relationship between light and the circadian system has long been a matter of discussion. Many studies have focused on entrainment of light with the internal biological clock. Light also functions as an environmental stimulus that affects the physiology and behaviour of animals directly. In this study, we used light as an unexpected stimulus for flies at different circadian times. We found that wildtype flies showed circadian changes in light-induced locomotion responses. Elevation of locomotor activity by light occurred during the subjective night, and performance in response to light pulses declined to trough during the subjective day. Moreover, arrhythmic mutants lost the rhythm of locomotion responses to light, with promotion of activity by light in timeless(01)mutants and inhibition of activity by light in Clock(ar)mutants. However, neither ablation of central oscillators nor disturbance of the functional clock inside compound eyes was sufficient to disrupt the rhythm of light responses. We show that, compound eyes, which have been identified as the control point for normal masking (promotion of activity by light), are sufficient but not necessary for paradoxical masking (suppression of activity by light) under high light intensity. This, taken together with the clear difference of light responses in wildtype flies, suggests that two different masking mechanisms may underlie the circadian modulation of light-induced locomotion responses.

A neurocomputational model of figure-ground discrimination and target tracking

A neurocomputational model is presented for figureground discrimination and target tracking. In the model, the elementary motion detectors of the correlation type, the computational modules of saccadic and smooth pursuit eye movement, an oscillatory neural-network motion perception module and a selective attention module are involved. It is shown that through the oscillatory amplitude and frequency encoding, and selective synchronization of phase oscillators, the figure and the ground can be successfully discriminated from each other. The receptive fields developed by hidden units of the networks were surprisingly similar to the actual receptive fields and columnar organization found in the primate visual cortex. It is suggested that equivalent mechanisms may exist in the primate visual cortex to discriminate figure-ground in both temporal and spatial domains.

A conserved role for phosphatidylinositol 3-kinase but not Akt signaling in mitochondrial adaptations that accompany physiological cardiac hypertrophy

Physiological cardiac hypertrophy is associated with mitochondrial adaptations that are characterized by activation of PGC-1alpha and increased fatty acid oxidative (FAO) capacity. It is widely accepted that phosphatidylinositol 3-kinase (PI3K) signaling to Akt1 is required for physiological cardiac growth. However, the signaling pathways that coordinate physiological hypertrophy and metabolic remodeling are incompletely understood. We show here that activation of PI3K is sufficient to increase myocardial FAO capacity and that inhibition of PI3K signaling prevents mitochondrial adaptations in response to physiological hypertrophic stimuli despite increased expression of PGC-1alpha. We also show that activation of the downstream kinase Akt is not required for the mitochondrial adaptations that are secondary to PI3K activation. Thus, in physiological cardiac growth, PI3K is an integrator of cellular growth and metabolic remodeling. Although PI3K signaling to Akt1 is required for cellular growth, Akt-independent pathways mediate the accompanying mitochondrial adaptations.

VEGF-D expression in lung adenocarcinoma with or without acquired resistance to gefitinib and normal lung

18166

Background: VEGF-D is related with pathogenesis and metastasis of lung cancer, however, its relationship with resistance to gefitinib in NSCLC remains unknown. Methods: Lung adenocarcinoma, normal lung tissues adjacent to the carcinoma and adenocarcinoma with acquired resistance to gefitinib including some metastastic lymph nodes were obtained during operation. Relative quantitation of VEGF-D gene expression was performed by SYBR Green real-time PCR with beta actin gene as the endogenous control. VEGF-D expression of each group was analyzed by comparing them qualitatively and quantitatively. The expression ratios were compared by Fisher’s exact test and expression levels were compared by two-related-samples nonparametric test. Results: CVEGF-D expression ratio of lung adenocarcinoma with acquired resistance to gefitinib (16.7%, 1/6) was not different from lung adenocarcinoma (50%, 7/14, P=0.325) but was significantly lower than that of normal lung (93.8%, 15/16, P=0.001). The logarithmically transformed VEGF-D relative expression levels in six lung adenocarcinomas and the matched normal lung tissues, which were 2.214±0.376 and 3.388±0.209, were found to be significantly different from each other by the analysis of Wilcoxon signed ranks test (P=0.028). Conclusions: VEGF-D expression is in a high-level state in normal lung tissues while in low-level or absent in lung adenocarcinoma with or without acquired resistance to gefitinib, suggesting that the role VEGF-D plays in normal lung tissue could be different from in lung adenocarcinoma with or without acquired resistance to gefitinib.

No significant financial relationships to disclose.

K-ras and EGFR mutations in 24 Chinese patients with non-small-cell lung cancer (NSCLC) treated with gefitinib

17109

Background: It was previously reported that K-ras mutations could behave as a resistance marker for response to gefitinib while EGFR mutations make NSCLC more responsive to this medication. And it is known that Asians and Westerners have different responses to gefitinib. Therefore, we are to identify the mutational status of K-ras and EGFR in the group of Chinese patients with NSCLC especially adenocarcinoma treated with gefitinib to find some helpful information. Methods: Genomic DNA was extracted from tumor specimens, including liquid nitrogen frozen tumor, paraffin blocks and fine needle biopsies from 24 patients with advanced NSCLC, who failed at least one platinum-based regimen, treated with gefitinib. Nested polymerase chain reaction products of codons 12, 13, 59, and 61 of K-ras and exon 18 through 21 of EGFR were directly sequenced at least twice. Results: Patients’ age ranges from 24 to 71 years (54.8 ± 10.2). Male/female was 14/10. Thirteen patients were smokers and 11 were non-smokers. Eighteen were adenocarcinomas, 2 were bronchioloalveolar carcinomas, 2 were squamous cell carcinomas and 2 were large cell carcinomas. The disease control (CR+PR+SD) rate was 79.2% (19/24) and the objective response (CR+PR) rate was 50.0% (12/24). No K-ras gene mutation was found in all patients. Fifteen patients (62.5%, 15/24) harbored EGFR mutations, which were delE746-A750 (8), delE746-A751 (1), delE746-A751insA (1), L861Q (1), L858R (5) and A871G (1). Two patients had double mutations (delE746-A750 and L858R). The disease control rate for wild type and mutant EGFR were 66.7% (6/9) and 86.7% (13/15), and the objective response rate were 33.3% (3/9) and 60.0% (9/15). Median time to progress (TTP) for wild type and mutant EGFR were 439 days (SE 249.8) and 367 days (SE 108.8). However, no statistically significant differences were found between these two groups regarding the response rates and TTP. Conclusions: K-ras mutation may occur at a low frequency in Chinese NSCLC groups despite the pathology, status of smoking, gender and EGFR mutations. And the relationship between the response to gefitinib and K-ras mutation might still remain to be determined at least in Chinese NSCLC. And the role of EGFR mutations in prediction of response to gefitinib should be further studied.

No significant financial relationships to disclose.

Detection of porcine circovirus type 2, porcine parvovirus and porcine pseudorabies virus from pigs with postweaning multisystemic wasting syndrome by multiplex PCR

Multiplex PCR was established to detect porcine circovirus type 2 (PCV-2), porcine parvovirus (PPV) and porcine pseudorabies virus (PRV) and applied to samples from 137 piglets exhibiting clinical signs of postweaning multisystemic wasting syndrome (PMWS). PCV-2 DNA was detected from all samples. Moreover, 43 samples were positive for PPV but negative for PRV; 11 samples were positive for PRV but negative for PPV; and 35 samples were positive both for PPV and PRV. These results suggests that PCV-2 co-infection with PRV and PPV may play an important role in PMWS. Also, multiplex PCR is an appropriate candidate method for diagnosis of PCV-2, PRV and PPV simultaneously in field cases.

Choice behavior of Drosophila facing contradictory visual cues

We studied the underlying neural mechanism of a simple choice behavior between competing alternatives in Drosophila. In a flight simulator, individual flies were conditioned to choose one of two flight paths in response to color and shape cues; after the training, they were tested with contradictory cues. Wild-type flies made a discrete choice that switched from one alternative to the other as the relative salience of color and shape cues gradually changed, but this ability was greatly diminished in mutant (mbm1) flies with miniature mushroom bodies or with hydroxyurea ablation of mushroom bodies. Thus, Drosophila genetics may be useful for elucidating the neural basis of choice behavior.

Neural representation of alpha-oriented moving light bars in the cortex: a neural network study

A neural computational model is suggested in this paper for investigating the stimulus dependence of spiking patterns and the neural representation of alpha-oriented moving light bars in the cortex. In this model, a stimulus-directed cortical developing algorithm is introduced for training the neural network. Three classes of computer simulations concerned with the orientation of the stimulus are carried out. The simulation results show that the fine temporal structure of spiking patterns of single units depends on the alpha orientation of the two moving light bars, and the fine temporal structure of their combinatorial spiking patterns are also context dependent. They also show that the neural representation of an alpha-oriented moving light bar is determined not only by the stimulus itself but also the architecture of the matured network. In the end, we propose a possible neural coding mechanism underlying the temporal cell subassemblies in the cortex, which could be spontaneously and dynamically organized into a dynamical cell assembly by synchronized activity of these subassemblies.

Fixing multiple waveguides induced by photorefractive solitons: directional couplers and beam splitters

We show how to transform multiple real-time photorefractive solitons into permanent two-dimensional single-mode waveguides impressed into the crystalline lattice of the host material. We experimentally demonstrate two specific configurations of such fixed multiple waveguides: directional couplers and multiple beam splitters.

Vanilloid receptor VR1 is both presynaptic and postsynaptic in the superficial laminae of the rat dorsal horn

Terminals in the rat spinal cord that express the vanilloid receptor VR1 are from small and medium dorsal root ganglion (DRG) neurons and appear prominent in lamina I and inner lamina II. Because primary afferents from these neurons can be myelinated or unmyelinated and their terminals in these laminae can be of various morphological and functional types, we undertook this study to identify the type(s) of VR1-positive afferent fibers and terminals. In the DRG, many small and medium-sized neurons are immunopositive. Under electron microscopy, dorsal root afferents that are immunopositive for VR1 are predominantly unmyelinated. Large numbers of VR1-positive terminals in lamina I are of the nonglomerular type and may contain dense core vesicles. VR1 immunoreactivity in terminals in lamina I is in good agreement with data on noxious, heat-sensitive neurons in the dorsal horn. Two types of glomerular afferent terminals in lamina II also are immunopositive for VR1. In both laminae, most VR1-positive terminals are distinct from substance P-positive terminals. However, the immunoreactivity in lamina II also is prominent in dendrites that are contacted by primary afferent endings. Because we also observed patchy immunostaining in cell bodies in lamina II, this unexpected result may reflect synthesis of VR1 by neurons in this lamina. However, because dorsal rhizotomy abolishes VR1 staining in both laminae I and II, it is suggested that the expression and intracellular dynamics of VR1 in lamina II neurons are controlled by presynaptic input.

Developmental shift of vanilloid receptor 1 (VR1) terminals into deeper regions of the superficial dorsal horn: correlation with a shift from TrkA to Ret expression by dorsal root ganglion neurons

The cloned vanilloid receptor VR1 can be activated by capsaicin and by thermal stimuli. The pattern of nerve terminals that contain VR1 in adult rat spinal cord does not correspond to axons that arise from a single subset of dorsal root ganglion neurons. Thus, we postulated that the basis underlying this complexity might be better understood from a developmental perspective. First, using capsaicin-induced hyperalgesia as a measure of VR1 function, we found that vanilloid receptors were functional as early as postnatal day 10 (P10), although hyperalgesia was of longer duration in adult. Interestingly, the appearance of VR1 protein in terminals of dorsal root ganglion neurons shifts over this postnatal period. From embryonic day 16 to P20, the majority of VR1 protein in the spinal cord was observed in lamina I. As animals matured, VR1 protein became more abundant in lamina II, particularly in the inner portion. Consistent with these observations, the number of dorsal root ganglion neurons coexpressing VR1 and isolectin B4 binding sites doubled while the number of neurons that had both VR1 and substance P remained relatively constant from P2 to P10. In peripheral processes, the number of VR1-positive nerve fibres and terminals in cutaneous structures in postnatal day 10 was half of that in adults. We also show that the association of VR1 with Ret is the reciprocal of the association of VR1 with Trk A. These results suggest that neurotrophins may regulate the extent to which populations of dorsal root ganglion neurons express VR1.