Skeletal muscle mass correlates with increased toxicity during neoadjuvant radiochemotherapy in locally advanced esophageal cancer: A SAKK 75/08 substudy.

BACKGROUND: Sarcopenia, the critical depletion of skeletal muscle mass, is an independent prognostic factor in several tumor entities for treatment-related toxicity and survival. In esophageal cancer, there have been conflicting results regarding the value of sarcopenia as prognostic factor, which may be attributed to the heterogeneous patient populations and the retrospective nature of previous studies. The aim of our study was therefore to determine the impact of sarcopenia on prospectively collected specific outcomes in a subgroup of patients treated within the phase III study SAKK 75/08 with trimodality therapy (induction chemotherapy, radiochemotherapy and surgery) for locally advanced esophageal cancer. METHODS: Sarcopenia was assessed by skeletal muscle index at the 3rd lumbar vertebra (L3) in cross-sectional computed tomography scans before induction chemotherapy, before radiochemotherapy and after neoadjuvant therapy in a subgroup of 61 patients from four centers in Switzerland. Sarcopenia was determined by previously established cut-off values (Martin et al., PMID: 23530101) and correlated with prospectively collected outcomes including treatment-related toxicity, postoperative morbidity, treatment feasibility and survival. RESULTS: Using the published cut-off values, the prevalence of sarcopenia increased from 29.5% before treatment to 63.9% during neoadjuvant therapy (p < 0.001). Feasibility of neoadjuvant therapy and surgery was not different in initially sarcopenic and non-sarcopenic patients. We observed in sarcopenic patients significantly increased grade ≥ 3 toxicities during chemoradiation (83.3% vs 52.4%, p = 0.04) and a non-significant trend towards increased postoperative complications (66.7% vs 42.9%, p = 0.16). No difference in survival according to sarcopenia could be observed in this small study population. CONCLUSIONS: Trimodality therapy in locally advanced esophageal cancer is feasible in selected patients with sarcopenia. Neoadjuvant chemoradiation increased the percentage of sarcopenia. Sarcopenic patients are at higher risk for increased toxicity during neoadjuvant radiochemotherapy and showed a non-significant trend to more postoperative morbidity.

Toxicity assessment of Clostridium difficile toxins in rodent models and protection of vaccination.

Clostridium difficile is the leading cause of hospital-acquired diarrhea, also known as C. difficile associated diarrhea. The two major toxins, toxin A and toxin B are produced by most C. difficile bacteria, but some strains, such as BI/NAP1/027 isolates, produce a third toxin called binary toxin. The precise biological role of binary toxin is not clear but it has been shown to be a cytotoxin for Vero cells. We evaluated the toxicity of these toxins in mice and hamsters and found that binary toxin causes death in both animals similar to toxins A and B. Furthermore, immunization of mice with mutant toxoids of all three toxins provided protection upon challenge with native toxins. These results support the concept that binary toxin contributes to the pathogenicity of C. difficile and provide a method for monitoring the toxicity of binary toxin components in vaccines.

Detecting and preventing reversion to toxicity for a formaldehyde-treated C. difficile toxin B mutant.

The toxicity of Clostridium difficile large clostridial toxin B (TcdB) can be reduced by many orders of magnitude by a combination of targeted point mutations. However, a TcdB mutant with five point mutations (referred to herein as mTcdB) still has residual toxicity that can be detected in cell-based assays and in-vivo mouse toxicity assays. This residual toxicity can be effectively removed by treatment with formaldehyde in solution. Storage of the formaldehyde-treated mTcdB as a liquid can result in reversion over time back to the mTcdB level of toxicity, with the rate of reversion dependent on the storage temperature. We found that for both the "forward" mTcdB detoxification reaction with formaldehyde, and the "reverse" reversion to toxicity reaction, mouse toxicity correlated with several biochemical assays including anion exchange chromatography retention time and appearance on SDS-PAGE. Maintenance of a low concentration of formaldehyde prevents reversion to toxicity in liquid formulations. However, when samples with 0.016% (v/v) formaldehyde were lyophilized and stored at 37 °C, formaldehyde continued to react with and modify the mTcdB in the lyophilized state. Lyophilization alone effectively prevented reversion to toxicity for formaldehyde-treated, formaldehyde-removed mTcdB samples stored at 37 °C for 6 months. Formaldehyde-treated, formaldehyde-removed lyophilized mTcdB showed no evidence of reversion to toxicity, appeared stable by several assays, and was immunogenic in mice, even after storage for 6 months at 37 °C.

Evaluating and adjusting for premature censoring of progression-free survival.

The intent-to-treat principle, grouping subjects as they were randomized and following all subjects to the endpoint or the end of study, allows valid statistical comparisons. Progression-free survival (PFS) has been used as a decision-making endpoint in oncology. It can be difficult to have a meaningful intent-to-treat analysis of PFS as some studies have extensive loss to follow-up for PFS. In the analysis, subjects lost to follow-up for PFS have their PFS times censored, with the censoring treated as noninformative. We use remaining overall survival to investigate whether premature censoring for PFS is informative and the potential bias in treating such censoring as noninformative.

The impact of sialic acids on the pharmacokinetics of a PEGylated erythropoietin.

Erythropoietin (EPO) is an important molecule in the erythropoiesis and various forms of EPO have been marketed in managing anemia in humans. Long acting EPOs for less frequent dosing have been generated either by increasing the number of glycosylation sites of the EPO molecule or by linking it to a polyethylene glycol (PEG). We have generated recombinant human EPO (rhEPO) using glycoengineered Pichia pastoris strains and evaluated the pharmacokinetics (PK) in rats of this molecule linked to a 40 kDa PEG (PEGylated rhEPO), in relation to its glycosylation patterns. As expected, the PEGylated rhEPO exhibited a significant improvement in half-life of serum when compared with the non-PEGylated version. Interestingly, the PK properties of the PEGylated rhEPO molecule were also significantly influenced by the glycosylation profile. Specifically, PEGylated rhEPO with a significantly higher sialic acid content in the biantennary structure (high A2) exhibited lower systemic clearance and higher systemic exposure than those with a lower sialic acid content (low A2) following either intravenous or subcutaneous administrations. These results suggest that A2 content may be one of the important criteria for release in manufacturing PEGylated rhEPO to ensure consistent PK.

Issues in using progression-free survival when evaluating oncology products.

Several challenging and often controversial issues arise in oncology trials with the use of the end point progression-free survival (PFS), defined to be the time to detection of progressive disease or death. While this end point does not directly measure how a patient feels, functions, or survives, it does provide insights about whether an intervention affects the tumor burden process, the intended mechanism through which it is hoped that most anticancer agents will provide benefit. However, simply achieving statistically significant effects on PFS is insufficient to obtaining reliable evidence of important clinical benefit, and even is insufficient to justifying the conclusion that the experimental intervention is "reasonably likely to provide clinical benefit." The magnitude of the effect on PFS in addition to the statistical strength of evidence is of great importance in interpreting the reliability of the evidence regarding clinical efficacy. PFS has several important properties, including being a direct measure of the effect of treatment on the tumor burden process, being sensitive to cytostatic as well as cytotoxic mechanisms of interventions, and incorporating the clinically relevant event of death, increasing its sensitivity to influential harmful mechanisms and avoiding substantial bias that arises when deaths are censored. To obtain reliable evidence about the effect of an intervention on PFS and patient survival, randomized trials should be conducted where all patients are followed to progression and death, and where patients in a control arm do not cross-in at progression unless the experimental regimen has already been established to be effective rescue treatment.

Missing data in biologic oncology products.

The intent-to-treat principle requires analyses according to the treatment groups to which patients were randomized and that patients be followed to the occurrence of the endpoint or the end of study. This provides unbiased comparisons with valid p values. For many trials the limitations of the data will not be known until the data are analyzed. In this article, the loss-to-follow-up with respect to the intent-to-treat principle on the most important efficacy endpoints was evaluated for clinical trials of anticancer biologic products submitted to the FDA from August 2005 to October 2008. We provide recommendations in light of the results.