The addition of Valproic acid to concurrent radiation therapy and temozolomide improves patient outcome: a Correlative analysis of RTOG 0525, SEER and a Phase II NCI trial.

PURPOSE/OBJECTIVES: Valproic Acid (VPA) is an antiepileptic agent with HDACi (histone deacetylase inhibitor) activity shown to radiosensitize glioblastoma (GBM) cells. We evaluated the addition of VPA to standard radiation therapy (RT) and temozolomide (TMZ) in an open-label, phase II study (NCI-06-C-0112). The intent of the current study was to compare our patient outcomes with modern era standard of care data (RTOG 0525) and general population data (SEER 2006-2013). MATERIALS/METHODS: 37 patients with newly diagnosed GBM were treated in a phase II NCI trial with daily VPA (25 mg/kg) in addition to concurrent RT and TMZ (2006 - 2013) and 411 patients with newly diagnosed GBM were treated in the standard TMZ dose arm of RTOG 0525 (2006 - 2008). Using the SEER database, adult patients (age > 15) with diagnostic codes 9440-9443 (third edition (IDC-O-3) diagnosed between 2006 - 2013 were identified and 6083 were included in the analysis. Kaplan-Meier method was used to estimate OS and PFS. The effect of patient characteristics and clinical factors on OS and PFS was analyzed using univariate analysis and a Cox regression model. A landmark analysis was performed to correlate recurrence to OS and conditional probabilities of surviving an additional 12 months at diagnosis, 6, 12, 18, 24 and 30 months were calculated for both the trial data and the SEER data. RESULTS: Updated median OS in the NCI cohort was 30.9m (22.2- 65.6m), compared to RTOG 0525 18.9m (16.8-20.3m) (p= 0.007) and the SEER cohort of 11m. Median PFS in the NCI cohort was 11.1m (6.6 - 49.6m) compared to RTOG 0525 with a median PFS of 7.5m (6.9-8.2m) (p = 0.004). Younger age, class V RPA and MGMT status were significant for PFS in both the NCI cohort and the RTOG 0525 cohort, in addition KPS was also significant for OS. In comparison to RTOG 0525, the population in the NCI cohort had a more favorable KPS and RPA, and a higher proportion of patients receiving bevacizumab after protocol therapy however with the exception of RPA (V) (8% vs 18%) (0.026), the effects of these factors on PFS and OS were not significantly different between the two cohorts. CONCLUSION: Previously reported improvements in PFS and OS with the addition of VPA to concurrent RT and TMZ in the NCI phase II study were confirmed by comparison to both a trial population receiving standard of care (RTOG 0525) and a contemporary SEER cohort. These results provide further justification of a phase III trial of VPA/RT/TMZ.

Statistical design of reverse dye microarrays.

MOTIVATION: In cDNA microarray experiments all samples are labelled with either Cy3 dye or Cy5 dye. Certain genes exhibit dye bias-a tendency to bind more efficiently to one of the dyes. The common reference design avoids the problem of dye bias by running all arrays 'forward', so that the samples being compared are always labelled with the same dye. But comparison of samples labelled with different dyes is sometimes of interest. In these situations, it is necessary to run some arrays 'reverse'-with the dye labelling reversed-in order to correct for the dye bias. The design of these experiments will impact one's ability to identify genes that are differentially expressed in different tissues or conditions. We address the design issue of how many specimens are needed, how many forward and reverse labelled arrays to perform, and how to optimally assign Cy3 and Cy5 labels to the specimens. RESULTS: We consider three types of experiments for which some reverse labelling is needed: paired samples, samples from two predefined groups, and reference design data when comparison with the reference is of interest. We present simple probability models for the data, derive optimal estimators for relative gene expression, and compare the efficiency of the estimators for a range of designs. In each case, we present the optimal design and sample size formulas. We show that reverse labelling of individual arrays is generally not required.

Latent class modeling approaches for assessing diagnostic error without a gold standard: with applications to p53 immunohistochemical assays in bladder tumors.

Improved characterization of tumors for purposes of guiding treatment decisions for cancer patients will require that accurate and reproducible assays be developed for a variety of tumor markers. No gold standards exist for most tumor marker assays. Therefore, estimates of assay sensitivity and specificity cannot be obtained unless a latent class model-based approach is used. Our goal in this article is to estimate sensitivity and specificity for p53 immunohistochemical assays of bladder tumors using data from a reproducibility study conducted by the National Cancer Institute Bladder Tumor Marker Network. We review latent class modeling approaches proposed by previous authors, and we find that many of these approaches impose assumptions about specimen heterogeneity that are not consistent with the biology of bladder tumors. We present flexible mixture model alternatives that are biologically plausible for our example, and we use them to estimate sensitivity and specificity for our p53 assay example. These mixture models are shown to offer an improvement over other methods in a variety of settings, but we caution that, in general, care must be taken in applying latent class models.

Biomechanical evaluation of osseous implants having different surface topographies in rats.

Biomechanical and biological factors can co-dependently influence the establishment of implant-tissue integration; thus, concurrent evaluation of these factors should provide a better understanding of osseointegration. This study aimed to establish and validate an in vivo rat model frequently used in molecular/cellular biology for implant biomechanical studies. We tested the hypotheses that the implant push-in test assesses the degree of osseointegration by the breakpoint load at the implant-tissue interface and that it sensitively differentiates between the effects of different implant surface topographies. The implant push-in test, which produces a consistent load-displacement measurement, was used to test miniature cylindrical titanium implants placed at the distal edge of the adult rat femur. The push-in test values obtained at each post-implantation healing point (weeks 0, 2, 4, and 8) significantly increased in a time-dependent manner. The implant surface after the push-in test was associated with remnant tissues containing host-derived elements, such as calcium, phosphate, and sulfate. In this model, acid-etched implants (average roughness, 0.159 microm) showed significantly greater push-in test values than did turned implants (average roughness, 0.063 microm) throughout the experimental period (p < 0.0001). These results support the validity of the push-in test in rats, which may be used as a rapid and sensitive biomechanical assay system for implant osseointegration research.

A class of permutation tests for stratified survival data.

We propose a class of permutation tests for stratified survival data. The tests are derived using the framework of Fay and Shih (1998, Journal of the American Statistical Association 93, 387-396), which creates tests by permuting scores based on a functional of estimated distribution functions. Here the estimated distribution function for each possibly right-, left-, or interval-censored observation is based on a shrinkage estimator similar to the nonparametric empirical estimator of Ghosh, Lahiri, and Tiwari (1989, Communications in Statistics--Theory and Methods 18, 121-146), and permutation is carried out within strata. The proposed test with a weighted Mann-Whitney functional is similar to the permutation form of the stratified log-rank test when there is a large strata effect or the sample size in each stratum is large and is similar to the permutation form of the ordinary log-rank test when there is little strata effect. Thus, the proposed test unifies the advantages of both the stratified and ordinary log-rank tests. By changing the functional, we may obtain a stratified Prentice-Wilcoxon test or a difference in means test with similar unifying properties. We show through simulations the advantage of the proposed test over existing tests for uncensored and right-censored data.

Latent model for correlated binary data with diagnostic error.

We propose a methodology for modeling correlated binary data measured with diagnostic error. A shared random effect is used to induce correlations in repeated true latent binary outcomes and in observed responses and to link the probability of a true positive outcome with the probability of having a diagnosis error. We evaluate the performance of our proposed approach through simulations and compare it with an ad hoc approach. The methodology is illustrated with data from a study that assessed the probability of corneal arcus in patients with familial hypercholesterolemia.

Antimony trichloride induces DNA damage and apoptosis in mammalian cells.

Antimony compounds are widely used in various manufacturing and semiconducting industries. Previously, it has been shown that antimony trichloride (SbCl3) elevates sister chromatid exchange (SCE) rates in V79 cells after a 28-h incubation. However, only limited data on its genotoxic effects are available so far. The present results demonstrate that a 4-h exposure to > 50 microM SbCl3 could induce micronuclei (MN) formation in cultured Chinese hamster ovary (CHO-K1) cells, human bronchial epithelial (BES-6) cells and human fibroblasts (HF). The order of sensitivity to SbCl3 determined by Sulforhodamine B (SRB)-staining survival assay is HF > BES-6 cells > CHO-K1 cells, with LD50 values in these cells being approximately 40, 80 and 180 microM, respectively. Apoptosis and DNA fragmentation was not found in cells immediately following 4-h SbCl3 treatment. However, DNA fragmentation was detected in CHO-K1 cells after 4-h SbCl3 treatment and a 16 h or more post incubation in fresh medium by 1.5% agarose gel electrophoresis. The delayed apoptosis was also observed under microscopic examination in HF, BES-6 and CHO-K1 cells after similar treatment protocol. In addition, an increase in calcium accumulation appeared in CHO-K1 cells and HF immediately after a 4-h SbCl3 treatment, or after a 24-h post incubation in fresh medium. The present results provide important genotoxic and cytotoxic information characterizing the cellular changes induced by short-term SbCl3 exposure in rodent and human cells.

Modeling multivariate discrete failure time data.

A bivariate discrete survival distribution that allows flexible modeling of the marginal distributions and yields a constant odds ratio at any grid point is proposed. The distribution can be extended to a multivariate distribution and is readily generalized to accommodate covariates in the marginal distributions and pairwise odds ratios. In addition, a pseudo-likelihood estimation procedure for estimating the regression coefficients in the marginal models and the association parameters in the pairwise odds ratios is presented. We evaluate the performance of the proposed estimation procedure through simulations. For bivariate data, pseudo-likelihood estimation of the association parameter has high efficiency. Loss of efficiency in the marginal regression coefficient estimates is small when the association is not strong. For both the marginal regression coefficients and the association parameter, coverage probabilities are close to the 95% nominal level. For multivariate data, the simulation results show that the parameter estimates are consistent. Coverage probability for the regression coefficient in the marginal model is close to the 95% nominal level but is slightly less than the nominal level for the association parameter. We illustrate the proposed methods using a subset of the Framingham Heart Study data where a significant positive association was found between the failure times of siblings.

Depressive personality: associations with DSM-III-R mood and personality disorders and negative and positive affectivity, 30-month stability, and prediction of course of Axis I depressive disorders.

The authors addressed 5 issues bearing on the validity of the construct of depressive personality disorder (DPD): its relationship with the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev.; American Psychiatric Association, 1987) mood and personality disorders and normal personality dimensions of negative and positive affectivity, its stability over 30-months, and its impact on the course of Axis I depressive disorders. Two samples were used: 156 outpatients with mood disorders, personality disorders, or both, and 267 of their 1st-degree relatives. The association between DPD and dysthymia was fairly modest, whereas the associations with major depression and the personality disorders were quite low. DPD was moderately correlated with both negative and positive affectivity; however, it contributed unique information beyond that available from the 2 emotional superfactors. Finally, DPD was moderately stable over a 30-month period and was associated with a poorer course of depression.

Tests of independence for bivariate survival data.

We propose two test statistics based on the covariance process of the martingale residuals for testing independence of bivariate survival data. The first test statistic takes the supremum over time of the absolute value of the covariance process, and the second test statistic is a time-weighted summary of the process. We derive asymptotic properties of the two test statistics under the null hypothesis of independence. In addition, we derive the asymptotic distribution of the weighted test and construct optimal weights for contiguous alternatives to independence. Through simulations, we compare the performance of the proposed tests and the inner product of the Savage scores statistics of Clayton and Cuzick (1985, Journal of the Royal Statistical Society, Series A 148, 82-108). These demonstrate that the supremum test is generally more powerful with comparatively little power loss relative to their test when Clayton's family alternative holds, and the weighted test is more powerful when the weight is appropriately chosen.

Inferences on the association parameter in copula models for bivariate survival data.

We investigate two-stage parametric and two-stage semi-parametric estimation procedures for the association parameter in copula models for bivariate survival data where censoring in either or both components is allowed. We derive asymptotic properties of the estimators and compare their performance by simulations. Both parametric and semi-parametric estimators of the association parameter are efficient at independence, and the parameter estimates in the margins have high efficiency and are robust to misspecification of dependency structures. In addition, we propose a consistent variance estimator for the semi-parametric estimator of the association parameter. We apply the proposed methods to an AIDS data set for illustration.

Sample size calculation for complex clinical trials with survival endpoints.

Sample size estimation is important in planning clinical trials. The purpose of this paper is to describe features and use of SIZE, a comprehensive computer program for calculating sample size, power, and duration of study in clinical trials with time-dependent rates of event, crossover, and loss to follow-up. SIZE covers a wide range of complexities commonly occurring in clinical trials, such as nonproportional hazards, lag in treatment effect, and uncertainties in treatment benefit. The use of SIZE is illustrated by several hypothetical examples as well as applications to real study designs, each featuring a statistical issue.

Assessing gamma frailty models for clustered failure time data.

Proportional hazards frailty models use a random effect, so called frailty, to construct association for clustered failure time data. It is customary to assume that the random frailty follows a gamma distribution. In this paper, we propose a graphical method for assessing adequacy of the proportional hazards frailty models. In particular, we focus on the assessment of the gamma distribution assumption for the frailties. We calculate the average of the posterior expected frailties at several followup time points and compare it at these time points to 1, the known mean frailty. Large discrepancies indicate lack of fit. To aid in assessing the goodness of fit, we derive and estimate the standard error of the mean of the posterior expected frailties at each time point examined. We give an example to illustrate the proposed methodology and perform sensitivity analysis by simulations.

Acute effects of oral pyridostigmine bromide on conditioned operant performance in rats.

Pyridostigmine bromide (Pyr), the current drug of choice in the management of myasthenia gravis, has been suggested for use in Alzheimer's dementia, and as a prophylactic treatment for intoxication with organophosphate cholinesterase inhibitors. The present study was undertaken to evaluate the dose-response and time-course effects of acute oral administration of Pyr over a broad dose range (3-40 mg/kg) on the lever pressing of rats maintained under a multiple fixed-ratio (FR-20) time-out schedule of reinforcement for water reward. The drug produced a dose-dependent biphasic response depression in the overall rate of FR responding. Low doses of Pyr (less than or equal to 12 mg/kg) that caused no gross signs of toxicity only moderately decreased rates of responding, primarily due to a decrease in response rates. Whereas high doses of Pyr (greater than 24 mg/kg) which produced overt signs of peripheral cholinergic intoxication markedly suppressed overall responding, primarily due to cessation of responding. The lowest effective dose of performance disruption was 6 mg/kg, and the ED50 was calculated as 23.3 (17.9-28.7) mg/kg. The time-course data of performance disruption showed that low doses of Pyr (less than or equal to 12 mg/kg) had an onset latency within 40-80 min and a duration of 20-80 min, whereas high doses (greater than or equal to 24 mg/kg) had an onset latency of 20-40 min and a duration greater than 80 min. These results suggest the recommended human therapeutic or prophylactic regimen of 30-120.mg Pyr, orally taken each 8 hours, might adversely affect behavioral performance.

Neurobehavioral effects of the pyridinium aldoxime cholinesterase reactivator HI-6.

A series of neurobehavioral testing procedures was used to evaluate the behavioral effects of the pyridinium aldoxime cholinesterase reactivator HI-6 in male Sprague-Dawley rats. These procedures were fixed-ratio (FR) responding, shuttle-box conditioned avoidance response (CAR), conditioned taste aversion (CTA), drinking behavior, open-field exploratory behavior, negative geotaxis, and wire suspension time. Dose-response studies of HI-6 at dose-levels of 25, 50 and 100 mg/kg, or saline (IP) were evaluated. HI-6 disrupted FR responding in a dose-dependent fashion, with significant effects occurring at doses of 50 and 100 mg/kg. The pattern of disruption was characterized by extended periods of nonresponding having an abrupt onset and offset. HI-6 produced CTA in a dose-related manner, with significant effects at doses equal to those that disrupted FR performance. HI-6 did not alter CAR, drinking motivation, exploratory behavior, negative geotaxis, or wire suspension time. These data suggest that there may be a commonality in the underlying mechanism(s) for the disruption in FR performance and the induction of the CTA. This mechanism may relate to the presumed drug-induced adverse internal state inducing the CTA.

Effect of the radioprotector WR-2721 on operant behavior in the rat.

The effect of WR-2721 on performance maintained by a fixed-ratio 20 (FR-20) schedule for water reinforcement was studied in male Sprague-Dawley rats. Graded doses of WR-2721 (range 25-100 mg/kg) were administered IP immediately prior to a 60 min test session. WR-2721 had a dose dependent monotonic disruptive effect on FR responding, with significant effects at doses of 50, 75 and 100 mg/kg. WR-2721 also decreased postsession water consumption, but only one significant effect at the highest dose (100 mg/kg). Both slopes of the dose-response regression line are parallel in effect. These data indicate that WR-2721 may affect drinking motivation, which could disrupt operant performance, and WR-2721 affects motor behavior at lower doses than those that depress "motivation" to drink. The log dose-probit analysis on the all-or-none disruptive pattern of pause of responding observed from cumulative records disclosed that the slope of this regression line (s = 1.11) was also almost identical to that of reinforcer decrement analyzed from graded dose-response relationship (s = 1.14) and shared the same estimated ED50's (58.5 and 55.6 mg/kg, respectively). A preliminary study using a variety of pharmacological interventions was also carried out to ascertain if the general functional gastrointestinal disorders produced by WR-2721 may subserve the behavioral deficits. Subcutaneous pretreatments with various selective, peripherally active, gastroprotective drugs [cimetidine (30 and 60 mg/kg), pirenzepine (5 and 10 mg/kg) and domperidone (1, 5 and 10 mg/kg)] 30 min prior to challenge with WR-2721 at dose of 100 mg/kg, demonstrated that these drugs did not yield any apparent significant attenuative effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between radioprotective and neuromotor effects of S-2(3-aminopropyl-amino)ethylphosphorothioate (WR-2721) in mice.

The radioprotective and neuromotor effects of WR-2721 were studied in male albino ICR strain mice. The protective activity was evaluated by graded doses of WR-2721 (50-400 mg/kg, IP) against whole body 60Co gamma irradiation at a single maximal lethal threshold dose rad (i.e., 1250 rad). The neuromotor effects of the drug were assayed by its action, at the same dose range as used in the protection assay, on spontaneous motor activity (SMA) and wire hanging performance (WHP). Drug doses were administered 30 min before radiation exposure and neurobehavioral testings. The results showed a dose-dependent increase in radioprotection and an inhibition in the neuromotor tasks. The radioprotective efficacy was seen at doses at which intrinsic neuromotor deficits were detected (100-400 mg/kg). A dose-related parallelism of protective efficacy and neurobehavioral toxicity (i.e., SMA inhibition and WHP disruption) was also observed. The present findings suggest that WR-2721 induces neuromotor dysfunctions along with its radioprotectivity.

Kinetic studies and structure-activity relationships of bispyridinium oximes as reactivators of acetylcholinesterase inhibited by organophosphorus compounds.

The kinetics of the reactivation of acetylcholinesterase inhibited by isopropyl methylphosphonofluoridate was studied. The reactivators used include nine bispyridinium monooximes and three bispyridinium dioximes. The dissociation constant (Kd) and the rate constant (k2) of dephosphorylation of the complex formed from the organophosphorus acetylcholinesterase (OP-AChE) and the oxime were measured. The reactivation parameters obtained from the in vitro kinetic studies were used to elucidate the structure-activity relationships. The hydrophobic property of a nonoxime substituent at the 3-position on the pyridinium ring can exert a positive effect on their binding affinity to OP-AChE. However, the rate constants (k2) of the nucleophilic displacement of OP-AChE by oximes depend negatively on these physical and structural factors of the oximes. The correlations of the in vivo antidotal efficacy (ED50) of these bispyridinium oximes have been analyzed with their pharmacological properties, e.g., reactivation potency, antimuscarinic activities, and antinicotinic activities. However, no satisfactory correlations were observed. It may be concluded that the detoxication mechanism of poisoning by isopropyl methylphosphonofluoridate is different from those of pinacolyl methylphosphonofluoridate and paraoxon.

Prevention of acute parathion and demeton poisoning in farmers around Shanghai.

After the occurrence of poisoning episodes among commune members who handled the insecticides parathion and demeton during the first few years of application in the early 1960s, a series of surveys was conducted and comprehensive regulatory actions were adopted. The surveys showed that the cause of most of the poisoning cases was percutaneous absorption of toxicant as a consequence of skin contamination during careless operating. As a result of a comprehensive program carried out by large numbers of administrators, health workers, and commune members, the incidence of intoxication quickly declined, starting in 1965, to a negligible level and has remained so to the present, even though parathion and demeton use has increased greatly. It is suggested that the experience obtained might be helpful to other areas in the People's Republic of China and in some developing countries.