Challenge of early screening liquid biopsy for cancer
Last Update: 2020-06-19
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Now we have advanced sequencing technology and computing toolsNext generation sequencing technology enables us to analyze cell-free tumor DNA (cfdna) in blood, while machine learning algorithm can find molecular characteristics of different cancer types from large data setsLiquid biopsies developed in combination with these techniques have been used to help patients with advanced cancer choose the best treatment and monitor cancer progression< br / > the development of early screening for cancer is a more ambitious goal for liquid biopsy researchersThere are many limitations in the current early screening and diagnosis methods: some are invasive, such as lung and breast tissue biopsy, and colonoscopy; while other detection methods may have higher false-positive results, so that they can only be used in the relatively high-risk populationFor example, for lung cancer, the history of smoking is an important factor in deciding whether to recommend individuals to receive CT scans to detect tumors< br / > liquid biopsy can theoretically fill in many gaps in the existing early screening and diagnosis methods, but before these tests become reality from ideal, they still need to overcome many challenges< br / > there are two main modes of early screening detection of cancer < br / > at present, the early screening detection of cancer in the development stage can be divided into two categories: one is Pan cancer detection, which can detect the presence of many kinds of cancerThis kind of detection needs to accurately determine the tissue origin of cancer while discovering cancerExamples of such early screening tests include early screening tests developed by grail and lunar tests developed by guardian healthAnother type of early screening tests uses more targeted detection methods to detect a small number of cancers or specific cancer typesFor example, freenome, based in San Francisco, California, is developing a liquid biopsy for early diagnosis of colorectal cancerThe early screening test for ovarian cancer and pancreatic cancer developed by the recently established thrive company was recognized as a breakthrough medical device by FDA last year< br / > deciding which early screening test to develop requires consideration of different factors, including the scientific basis of early screening test and the unmet needs of specific cancer patientsFreenome, for example, chose to develop early screening for colorectal cancer for a very direct reason"Colonoscopy has shown that the detection of precancerous lesions in the early stage of cancer has a significant impact on the treatment of colorectal cancerThe earlier the diagnosis is made, the longer the patient's life span, which is why we chose colorectal cancer" Said DrJimmy Lin, chief scientific officer of the company< br / > and Grail's early screening test can detect more than 20 cancers in one testThese include 12 deadly cancer types, which cause two-thirds of cancer deathsThis major unmet medical need is the reason for grail to develop early detection of Pan cancer< br / > how to prevent false positive in early screening test? < br / > there are two key indicators in the evaluation of early screening: specificity and sensitivitySensitivity refers to the proportion of positive patients found in the population, while specificity refers to the proportion of positive patients found in the testIf no cancer patients are tested positive for cancer, then these positive patients are called false positive patients< br / > for early screening, it is very important to minimize the proportion of false positive resultsBecause false positive results will lead to patients to accept more unnecessary follow-up tests, and these tests will bring more physical, mental and economic burden to patientsIndustry experts said that the false-positive rate of a successful early screening test should be less than 1%To achieve this goal, we need to optimize the detection based on large-scale test dataAnother strategy is to add other biomarkers to improve the specificity of detection besides cfdna< br / >The company's circulating cell free Genome Atlas (CCGA) study is a prospective, observational longitudinal study to describe the characteristics of cancer genome signals in the blood of cancer patients and healthy volunteersThe study involved 15000 participants The company's strong study recruited 100000 women who needed mammograms The company's summit study will recruit about 50000 elderly volunteers aged 50-77 who were not diagnosed with cancer at the time of registration < br / > Said Ms Kelsey Grossman of grail < br / > due to the complexity of cancer, in order to improve the specificity of detection, early screening usually uses other biomarkers to assist the detection of DNA fragments For example, Grail's early screening tests use DNA methylation information to optimize the tests This optimized early screening test has been recognized by FDA as a breakthrough medical device Grail also announced the excellent results of this test at the recent annual meeting of the American Society of clinical oncology Its specificity is more than 99%, and the average sensitivity is 76% < br / > while cancer eek pan cancer early detection of thrive company not only detects the presence of more than 60 DNA sequences related to 8 specific cancers, but also detects the presence of 8 protein biomarkers related to cancer Research published in Science in 2018 shows that this early screening test can be used for early diagnosis of 8 types of cancer with more than 99% specificity and 70% sensitivity < br / > can early screening improve the prognosis of patients? < br / > it seems a natural conclusion that early detection of cancer by early screening should allow patients to live longer However, there is not much scientific evidence to support this conclusion This is not only a problem for early screening liquid biopsy, but also a problem for other early screening tests For example, mammography is the standard method for early screening of breast cancer, but its impact on the survival of patients is still a controversial topic In the field of colorectal cancer and ovarian cancer, scientific research has shown that screening and screening for colonoscopy and cervical smear tests have made important contributions to the decline of the incidence rate and mortality rate of these two types of cancer < br / > it's too early for early screening liquid biopsies to prove that they can help save lives, and researchers now aim to prove that they can detect cancer earlier Because liquid biopsies are less invasive, patients are more likely to be screened early, so they can play a greater role in the detection of cancer "If we can improve patients' compliance with early screening tests, many lives will be saved "One of the co founders of guardian health, Dr Amir Ali talasaz, said < br / > for all R & D personnel who develop cancer early screening liquid biopsy, their common ideal is: in the future, cancer early screening test will become a part of the annual routine physical examination With only one or two tubes of blood, cancer can be screened just like cholesterol With the performance of early screening liquid biopsy getting better and better, more and more clinical evidences are collected by researchers, and this ideal may become a reality sooner < br / > reference materials: < br / >  better on blood Retrieved June 24, 2019, from < br / >  5 questions facing companies developing liquid biopsies for cancer screening Retrieved June 24, 2019, from < br / >  cancer? This researcher says he can see it in your blood Retrieved June 24, 2019, from < br / >, How far are we from success?
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