Predicting response to bevacizumab in ovarian cancer: a panel of potential biomarkers informing treatment selection.

PURPOSE: The aim of this study was to identify and validate novel predictive and/or prognostic serum proteomic biomarkers in patients with epithelial ovarian cancer (EOC) treated as part of the phase III international ICON7 clinical trial. EXPERIMENTAL DESIGN: ICON7 was a phase III international trial in EOC which showed a modest but statistically significant benefit in progression-free survival (PFS) with the addition of bevacizumab to standard chemotherapy. Serum samples from 10 patients who received bevacizumab (five responders and five nonresponders) were analyzed by mass spectrometry to identify candidate biomarkers. Initial validation and exploration by immunoassay was undertaken in an independent cohort of 92 patients, followed by a second independent cohort of 115 patients (taken from across both arms of the trial). RESULTS: Three candidate biomarkers were identified: mesothelin, fms-like tyrosine kinase-4 (FLT4), and α1-acid glycoprotein (AGP). Each showed evidence of independent prognostic potential when adjusting for high-risk status in initial (P < 0.02) and combined (P < 0.01) validation cohorts. In cohort I, individual biomarkers were not predictive of bevacizumab benefit; however, when combined with CA-125, a signature was developed that was predictive of bevacizumab response and discriminated benefit attributable to bevacizumab better than clinical characteristics. The signature showed weaker evidence of predictive ability in validation cohort II, but was still strongly predictive considering all samples (P = 0.001), with an improvement in median PFS of 5.5 months in signature-positive patients in the experimental arm compared with standard arm. CONCLUSIONS: This study shows a discriminatory signature comprising mesothelin, FLT4, AGP, and CA-125 as potentially identifying those patients with EOC more likely to benefit from bevacizumab. These results require validation in further patient cohorts.

A comparison of the analytical performance of five commercially available assays for neutrophil gelatinase-associated lipocalin using urine.

BACKGROUND: Neutrophil gelatinase-associated lipocalin (NGAL) is a promising biomarker for acute kidney injury that is beginning to be used in clinical practice in addition to research studies. The current study describes an independent validation and comparison of five commercially available NGAL assays, focusing on urine samples. This is an essential step in the translation of this marker to clinical use in terms of allowing valid inter-study comparison and generation of robust results. METHODS: Two CE (Conformité Européenne)-marked assays, the NGAL Test (BioPorto) on Siemens ADVIA(®) 1800 and the ARCHITECT Urine NGAL assay on i2000SR (Abbott Laboratories), and three research-use-only (RUO) ELISAs (R&D Systems, Hycult and BioPorto) were evaluated. Imprecision, parallelism, recovery, selectivity, limit of quantitation (LOQ), vulnerability to interference and hook effect were assessed and inter-assay agreement was determined using 68 urine samples from patients with various renal diseases and healthy controls. RESULTS: The Abbott and R&D Systems assays demonstrated satisfactory performance for all parameters tested. However for the other three assays evaluated, problems were identified with LOQ (BioPorto/ADVIA(®)), parallelism (BioPorto ELISA) or several parameters (Hycult). Between-method agreement varied with the Hycult assay in particular being markedly different and highlighting issues with standardization and form of NGAL measured. CONCLUSIONS: Variability exists between the five NGAL assays in terms of their performance and this should be taken into account when interpreting results from the various clinical or research studies measuring urinary NGAL.

Measuring carbonic anhydrase IX as a hypoxia biomarker: differences in concentrations in serum and plasma using a commercial enzyme-linked immunosorbent assay due to influences of metal ions.

BACKGROUND: There is increasing interest in measuring the soluble forms of carbonic anhydrase IX (CA IX) in blood as a marker of hypoxia for prognostic purposes or for predictive use in therapeutic trials in various cancers. Following our initial observations of marked differences in the measured concentrations of CA IX in EDTA plasma versus serum, we sought to investigate these further in order to determine their effects on results in published studies and to ensure accurate measurement in future studies. METHODS: Serum and EDTA plasma samples from healthy controls and patients with renal cancer were used in the validation of two commercially available enzyme-linked immunosorbent assays (ELISAs) for CA IX with examination of recovery, parallelism and specificity and comparison of paired plasma and serum. RESULTS: Successful validation of one of the ELISAs was not achieved with particular problems with parallelism and marked differences in measured CA IX concentrations between EDTA plasma and serum. This appeared to be due to a metal ion-dependent epitope on CA IX recognized by the detection antibody in this assay. The other commercially available ELISA examined was successfully validated and showed no difference in CA IX between EDTA plasma and serum. CONCLUSIONS: These results have important consequences for published studies using this assay where the conclusions drawn from the measurements made may be invalid. This study highlights the need for stringent validation of commercially available assays, including examination of various sample types, before use in research studies.