This article defines and describes best practices for the academic and business community to generate evidence of clinical utility for cancer molecular diagnostic assays. Beyond analytical and ...clinical validation, successful demonstration of clinical utility involves developing sufficient evidence to demonstrate that a diagnostic test results in an improvement in patient outcomes. This discussion is complementary to theoretical frameworks described in previously published guidance and literature reports by the U.S. Food and Drug Administration, Centers for Disease Control and Prevention, Institute of Medicine, and Center for Medical Technology Policy, among others. These reports are comprehensive and specifically clarify appropriate clinical use, adoption, and payer reimbursement for assay manufacturers, as well as Clinical Laboratory Improvement Amendments-certified laboratories, including those that develop assays (laboratory developed tests). Practical criteria and steps for establishing clinical utility are crucial to subsequent decisions for reimbursement without which high-performing molecular diagnostics will have limited availability to patients with cancer and fail to translate scientific advances into high-quality and cost-effective cancer care. See all articles in this CCR Focus section, "The Precision Medicine Conundrum: Approaches to Companion Diagnostic Co-development."
The focus of treating an individual patient is the identification of the individual's specific needs. The measurement of the patient's characteristics, such as blood pressure or body temperature, and ...also the measurement of biomarkers, such as cholesterol or hemoglobin A1C is part of the patient's health assessment. The deeper the insights into the phenotypic and molecular characteristics of the patient, the better we are positioned to treat a patient. Increasingly, this assessment includes testing for certain pharmacologically relevant genetic variations (pharmacogenetics). Evaluating how the patient's genetic makeup combined with the patient's exposure to environmental influences could impact disease and treatment decisions is becoming the cornerstone of personalized medicine. However, we often use such assessments for finding the most ‘effective’ treatment, but we might not always be as rigorous in our assessment of potential safety risks. This is particularly apparent when looking at how safety risks are communicated. Often this information is only available as general, population-based statements and a small amount of information is available to evaluate whether or not an individual patient is at risk. Although pharmacogenetic tests that can help to assess whether an individual patient's personal risk exist (safety pharmacogenetics), they are not always performed.
The past decade of pharmacogenomics was driven by the sequencing of the human genome to create ever denser maps of genetic variations for studying the diversity across individuals. Today, genotyping ...technology is available at a fraction of the cost of what it was 10 years ago and many pharmacogenomic variations have been studied in detail. Still, we are only starting to gain an understanding of how pharmacogenomic-guided drug therapy affects clinical outcomes: real-world studies that demonstrate the clinical effectiveness and address the economic implications of pharmacogenomics are needed to help decide when and how to implement pharmacogenomics in clinical practice, how to regulate pharmacogenomic testing and how the healthcare system will integrate this new science into an environment of rapidly increasing cost.
In light of the meeting of the US Food and Drug Administration (FDA) in March 2011 to discuss the regulation of clinical direct-to-consumer (DTC) genetic tests, we have invited five experts to ...consider the best means of overseeing the ordering and interpretation of these tests. Should these tests be regulated? If so, who, if anyone, should communicate results to consumers?
Microarray-based measurement of mRNA abundance assumes a linear relationship between the fluorescence intensity and the dye concentration. In reality, however, the calibration curve can be nonlinear.
...By scanning a microarray scanner calibration slide containing known concentrations of fluorescent dyes under 18 PMT gains, we were able to evaluate the differences in calibration characteristics of Cy5 and Cy3. First, the calibration curve for the same dye under the same PMT gain is nonlinear at both the high and low intensity ends. Second, the degree of nonlinearity of the calibration curve depends on the PMT gain. Third, the two PMTs (for Cy5 and Cy3) behave differently even under the same gain. Fourth, the background intensity for the Cy3 channel is higher than that for the Cy5 channel. The impact of such characteristics on the accuracy and reproducibility of measured mRNA abundance and the calculated ratios was demonstrated. Combined with simulation results, we provided explanations to the existence of ratio underestimation, intensity-dependence of ratio bias, and anti-correlation of ratios in dye-swap replicates. We further demonstrated that although Lowess normalization effectively eliminates the intensity-dependence of ratio bias, the systematic deviation from true ratios largely remained. A method of calculating ratios based on concentrations estimated from the calibration curves was proposed for correcting ratio bias.
It is preferable to scan microarray slides at fixed, optimal gain settings under which the linearity between concentration and intensity is maximized. Although normalization methods improve reproducibility of microarray measurements, they appear less effective in improving accuracy.
The field of pharmacogenetics will soon celebrate its 50th anniversary. Although science has delivered an impressive amount of information in these 50 years, pharmacogenetics has suffered from lack ...of integration into clinical practice. There are several reasons for this, including the unmet need for education at medical schools and the lack of awareness about the impact of genetic medicine on healthcare in the community. Recently, the FDA announced that it considers pharmacogenomics one of three major opportunities on the critical path to new medical products. This notion by the FDA is filling the regulatory void that existed between drug developers and drug users. However, in order to bring pharmacogenetic testing to the prescription pad successfully, healthcare professionals and policy makers, as well as patients, need to have the necessary background knowledge for making educated treatment decisions. To effectively move pharmacogenetics into everyday medicine, it is therefore imperative for scientists and teachers in the field to take on the challenge of disseminating pharmacogenetic insights to a broader audience.
The FDA Guidance for Industry: Pharmacogenomics Data Submissions was issued in 2005. This guidance document covers a broad area associated with how and when to submit genomic data to the FDA. ...Additional tasks associated with genomic data submissions include the implementation of genomic data submissions; the process for qualification of exploratory biomarkers into valid biomarkers; and technical recommendations for the generation and submission of genomic data to the FDA. These tasks have been addressed throughout the past 2 years by a number of initiatives. These initiatives have included the development of the Interdisciplinary Pharmacogenomics Review Group for review of pharmacogenomic data submissions, the pilot process for qualification of biomarkers, and the concept paper on recommendations for the generation and submission of genomic data. These initiatives have contributed to the effective implementation of the Pharmacogenomics Guidance at the FDA. Environ. Mol. Mutagen. 48:354–358, Published 2007 Wiley‐Liss, Inc.
One mechanism by which cells adapt to environmental changes is by altering gene expression. Here, we have used cDNA microarrays to identify genes whose expression is altered by exposure to the ...environmental contaminant 2,3,7,8-tetrachlorodibenzo-
p-dioxin (TCDD). The goal of our study was to enhance our understanding of toxicity mediated through the pathway by which TCDD stimulates gene expression. To model this toxicity response, we exposed human hepatoma (HepG2) cells to TCDD (10 nM for 18 h) and analyzed mRNA by two-color fluorescent hybridization to cDNA sequences immobilized on glass microscope slides (2.5×7.5 cm) covering a surface area of 2.25 cm
2. We analyzed approximately one-third of the genes expressed in HepG2 cells and found that TCDD up- or down-regulates 112 genes two-fold or more. Most changes are relatively subtle (two- to four-fold). We verified the regulation of protooncogene cot, XMP, and human enhancer of filamentation-1 (HEF1), genes involved in cellular proliferation, as well as metallothionein, plasminogen activator inhibitor (PAI1), and HM74, genes involved in cellular signaling and regeneration. To characterize the response in more detail, we performed time-course, dose-dependence studies, and cycloheximide experiments. We observed direct and indirect responses to TCDD implying that adaptation to TCDD (and other related environmental stimuli) is substantially more complex than we previously realized.
We surveyed 10,303 United States physicians on where they obtain pharmacogenomic testing information. Thirty-nine percent indicated that they obtained this from drug labeling. Factors positively ...associated with this response included older age, postgraduate instruction, using other information sources, regulatory approval/ recommendation of testing, reliance on labeling for information, and perception that patients have benefited from testing. Physicians use pharmacogenomic testing information from drug labeling, highlighting the importance of labeling information that is conducive to practice application.
Over the past five years, denaturing high-performance liquid chromatography (DHPLC) has emerged as one of the most versatile technologies for the analysis of genetic variations. With the benefit of ...novel polymer chemistries used for separation, the accuracy, sensitivity, and the throughput of DHPLC for DNA and RNA analysis have greatly improved. DHPLC has been adopted in many laboratories for the screening of mutations and single-nucleotide polymorphisms (SNPs). The ability of DHPLC to detect known and unknown mutations simultaneously has put this technology at the forefront of genetic analysis for a wide variety of diseases. In addition, the high sensitivity of DHPLC combined with the accuracy of the heteroduplex analysis has allowed the development of applications beyond the scope of traditional sequencing or genotyping, e.g., the early detection of cancer. This article reviews the methods, which made DHPLC a widely used tool for diagnosis in molecular genetics and pharmacogenetics. The article provides an overview of current applications in these fields and points to novel applications in areas like epigenetics and the analysis of heteroplasmic mitochondrial DNA, in which DHPLC is becoming the leading technology.
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