An analysis of institutional effects in a multicenter cancer clinical trial: is it also plausible from the clinicians' point of view?

Handling dropout and clustering in longitudinal multicentre clinical trials

Many clinical trials enrol patients from different medical centres. Multi-centre studies are particularly helpful in cancer research as they allow researchers to evaluate the efficacy of a therapy in a variety of patients and settings, making it possible to investigate the effect of treatments in those cases when it is difficult, or even impossible, for a single centre to recruit the required number of patients. It is often argued, however, that despite agreement among different centres to follow common standardized protocols, variation may occur in both baseline characteristics of the recruited patients and in treatment effects. This heterogeneity should be detected and, if present, accounted for in the data analysis. Furthermore, the longitudinal nature of these types of experimental studies raises the problem of attrition, that is, patients may dropout of the study for a number of reasons mainly death or disease progression. In this paper, we consider the health related quality of life of advanced melanoma patients in a longitudinal multi-centre randomized clinical trial comparing two different anti-tumoural treatments. We propose a Heckman type model to account for the possibility that patients dropout according to a non-ignorable mechanism. The model is extended to a multilevel setting to account both for the longitudinal nature and the multi-centre structure of the design. We found a strong variation across centres in the quality of life evaluation. The effect of centres on the dropout was not found to be relevant in the considered data although dropout does depend on patient′s characteristics.

Modelling the distribution of health-related quality of life of advanced melanoma patients in a longitudinal multi-centre clinical trial using M-quantile random effects regression

Health-related quality of life assessment is important in the clinical evaluation of patients with metastatic disease that may offer useful information in understanding the clinical effectiveness of a treatment. To assess if a set of explicative variables impacts on the health-related quality of life, regression models are routinely adopted. However, the interest of researchers may be focussed on modelling other parts (e.g. quantiles) of this conditional distribution. In this paper, we present an approach based on quantile and M-quantile regression to achieve this goal. We applied the methodologies to a prospective, randomized, multi-centre clinical trial. In order to take into account the hierarchical nature of the data we extended the M-quantile regression model to a three-level random effects specification and estimated it by maximum likelihood.

Blockade of the receptor for advanced glycation end products attenuates acetaminophen-induced hepatotoxicity in mice

BACKGROUND AND AIM

Severe injury to the liver, such as that induced by toxic doses of acetaminophen, triggers a cascade of events leading to hepatocyte death. It is hypothesized that activation of the receptor for advanced glycation end products (RAGE) might contribute to acetaminophen-induced liver toxicity by virtue of its ability to generate reactive oxygen species, at least in part via nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and thereby activate downstream signaling pathways leading to cellular injury.

METHODS

A model was employed in which toxic doses of acetaminophen (1125 mg/kg) were administered to C57BL/6 mice. To block RAGE, mice received murine soluble (s) RAGE, the extracellular ligand binding domain of the receptor that acts as a decoy to interrupt ligand-RAGE signaling.

RESULTS

Animals treated with sRAGE displayed increased survival compared with vehicle treatment, and markedly decreased hepatic necrosis. Consistent with an important role for RAGE-triggered oxidant stress in acetaminophen-induced injury, a significant reduction of nitrotyrosine protein adducts was observed in hepatic tissue in sRAGE-treated versus vehicle-treated mice receiving acetaminophen, in parallel with significantly increased levels of glutathione. In addition, pro-regenerative cytokines tumor necrosis factor-alpha and interleukin-6 were increased in sRAGE-treated versus vehicle-treated mice.

CONCLUSION

These findings implicate RAGE-dependent mechanisms in acetaminophen-induced liver damage and suggest that blockade of this pathway may impart beneficial effects in toxin-induced liver injury.

Exogenous IL-6 inhibits acute inflammatory responses and prevents ischemia/reperfusion injury after intestinal transplantation

Interleukin-6 (IL-6) is a pleiotropic acute reactant cytokine involved in inflammatory responses. To explore the role of IL-6 in inflammation, this study examined the efficacy of exogenous IL-6 in preventing intestinal ischemia/reperfusion (I/R) injury associated with small bowel transplantation (SBTx). Syngenic orthotopic SBTx was performed in Lewis rats after 6-h graft preservation in University of Wisconsin (UW) at 4 degrees C. IL-6 mutein (IL-6m, 500 microg/kg), a recombinant molecular variant of human IL-6, was subcutaneously given to donors 2 h before harvesting (IL-6mD) or to excised grafts by luminal infusion (IL-6mG). Animal survival was 100% and 75% in IL-6mD (p<0.05 vs. control) and IL-6mG groups, respectively, compared with 64.3% in untreated controls. The severity of I/R injury (e.g. epithelial denudation, villous congestion) was reduced with IL-6m, in addition to a striking increase in re-epithelization. With IL-6m, neutrophil extravasation was markedly reduced in intestinal grafts and in remote organs (e.g. lung). IL-6m mediated anti-inflammatory effects through the inhibition of I/R-induced up-regulation of intragraft and circulating IL-1-beta, tumor necrosis factor-alpha (TNF-alpha) and IL-6. IL-6m also increased intestinal graft tissue blood flow. These results show that IL-6 is effective in protecting the intestine from cold I/R injury by maintaining graft blood flow and reducing pro-inflammatory cytokine up-regulation and neutrophil infiltration.

Site-characteristic expression and induction of trefoil factor family 1, 2 and 3 and malignant brain tumor-1 in normal and diseased intrahepatic bile ducts relates to biliary pathophysiology

BACKGROUND/AIM

Trefoil factor family (TFF)1,2,3 are involved in a homeostasis/repair process of mucosal epithelia. In this study, the significance of TFF family and deleted in the malignant brain tumor-1 (DMBT1), a putative receptor of TFF2, in the intrahepatic biliary tree was investigated in normal and diseased livers.

MATERIALS AND METHODS

Expression of TFF1,2,3 and DMBT1 were examined immunohistochemically in primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC), chronic viral hepatitis (CVH), extrahepatic biliary obstruction (EBO), and normal livers.

RESULTS

In normal livers, TFF1,3 and DMBT1 were infrequently detectable in large and rarely in small bile ducts, respectively. TFF2 was not detectable in large bile ducts. In large bile duct diseases (PSC and EBO), expression of TFF3 and DMBT1 were increased. In small bile duct diseases (PBC and CVH), expression of TFF2/DMBT1 was induced in moderately to severely damaged ducts irrespective of etiology.

CONCLUSION

The intrahepatic biliary tree shows a site-characteristic expression and induction of TFF1,2,3 and DMBT1. In large bile ducts, TFF1,3 were constitutively expressed and increased in pathologic bile ducts. In small bile ducts, TFF2/DMBT1 is induced in damaged ducts irrespective of etiologies. However, the cytoprotective/repair property of TFF2/DMBT1 may not be enough to prevent the following bile duct loss in PBC.

Proportional hazards models with random effects to examine centre effects in multicentre cancer clinical trials

In randomized clinical trials comparing treatment effects on diseases such as cancer, a multicentre trial is usually conducted to accrue the required number of patients within a reasonable period of time. The fundamental point of conducting a multicentre trial is that all participating investigators must agree to follow the common study protocol. However, even with every attempt having been made to standardize the methods for diagnosing severity of disease and evaluating response to treatment, for example, they might be applied differently at different centres, and these may vary from comprehensive cancer centres to university hospitals to community hospitals. Therefore, in multicentre trials there is likely to be some degree of variation (heterogeneity) among centres in both the baseline risks and the treatment effects. While we estimate the overall treatment effect using a summary measure such as hazard ratio and usually interpret it as an average treatment effect over the centre, it is necessary to examine the homogeneity of the observed treatment effects across centres, that is, treatment-by-centre interaction. If the data are reasonably consistent with homogeneity of the observed treatment effects across centres, a single summary measure is adequate to describe the trial results and those results will contribute to the scientific generalization, the process of synthesizing knowledge from observations. On the other hand, if heterogeneity of treatment effects is found, we should carefully interpret the trial results and investigate the reason why the variation is seen. In the analyses of multicentre trials, a random effects approach is often used to model the centre effects. In this article, we focus on the proportional hazards models with random effects to examine centre variation in the treatment effects as well as the baseline risks, and review the parameter estimation procedures, frequentist approach-penalized maximum likelihood method--and Bayesian approach--Gibbs sampling method. We also briefly review the models for bivariate responses. We present a few real data examples from the biometrical literature to highlight the issues.