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Cancer Genetics Overview (PDQ®): Genetics - Health Professional Information [NCI] - Clinical Sequencing

Introduction

Broad-scale genome sequencing approaches, including multigene panel testing, whole-exome sequencing (WES), and whole-genome sequencing (WGS), are rapidly being developed and incorporated into a spectrum of clinical oncologic settings, including cancer therapeutics and cancer risk assessment. Several institutions and companies offer tumor sequencing, and institutions are developing "precision medicine" programs that sequence tumor genomes to identify driver genetic alterations that are targetable for therapeutic benefit to patients.[1,2,3] Many of these tumor-based approaches use reference germline DNA sequences to identify pathogenic alterations, which can also provide information on inherited risk of cancers in families. In the genetic counseling and cancer risk assessment –setting, the use of gene panel testing to evaluate inherited cancer risk is becoming more common and may become routine in the near future, with institutions and companies offering gene panel testing to detect alterations in a host of cancer risk–associated genes.

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This complementary and alternative medicine (CAM) information summary provides an overview of the use of PC-SPES as a treatment in people with cancer. The summary includes a brief history of PC-SPES research, the results of clinical trials, and possible adverse effects of PC-SPES. Included in this summary is a discussion of the contamination of PC-SPES and its withdrawal from avenues of distribution. This summary contains the following key information: PC-SPES is a patented mixture of eight...

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These advances in gene sequencing technologies also identify alterations in genes related to the primary indication for ordering genetic sequence testing, along with findings not related to the disorder being tested. The latter genetic findings, termed incidental or secondary findings, are currently a source of significant clinical, ethical, legal, and counseling debate. This section was created to provide information about genomic sequencing technologies in the context of clinical sequencing and highlights additional areas of clinical uncertainty for which further research and approaches are needed.

Background

DNA sequencing technologies have undergone rapid evolution, particularly since 2005 when massively parallel sequencing, or next-generation sequencing (NGS), was introduced.[4]

Automated Sanger sequencing is considered the first generation of sequencing technology.[5] Sanger cancer gene sequencing uses polymerase chain reaction (PCR) amplification of genetic regions of interest followed by sequencing of PCR products using fluorescently labeled terminators, capillary electrophoresis separation of products, and laser signal detection of nucleotide sequence.[6,7] While this is an accurate sequencing technology, the main limitations of Sanger sequencing include low throughput, a limited ability to sequence more than a few genes at a time, and the inability to detect structural rearrangements.[6]

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