- A blood test for cancer that examines the methylation of cell-free DNA has been developed by researchers.
- To find out how the Gallieri test, as it is known, affects the time it takes to diagnose cancer, a significant trial is now being conducted.
- A recent meeting featured the presentation of certain trial findings.
- In contrast to false negatives, they have a high proportion of false positives.
Cancer is more curable and patients are likely to live longer when it is discovered sooner.
In order to better diagnose cancer before symptoms show, national screening programs have been devised, although not all malignancies are covered by them.
The screening programs’ ability to identify enough cancer cases to be useful and if they identify too many false positive findings in healthy individuals are also subjects of debate.
Like breast cancer mammography screening, several cancer screening tests are developed to check for a tumor in a specific organ. The prostate-specific antigen used in prostate cancer screening is an example of a screening test that also looks for a specific cancer signal from a specific organ.
Signature of cancerous methylation
When genes involved in DNA repair, cell division, or death are expressed differently in malignant cells, the cells proliferate out of control and form tumors.
Methyl groups, which are found in all human cells’ DNA, have an impact on the transcription and translation of the DNA. These are frequently different in cancer cells and help the cell’s gene expression to alter.
In 1948, scientists also learned that all human cells, both healthy and malignant ones, release what is known as cell-free DNA into circulation.
In noninvasive prenatal testing, blood tests employing cell-free DNA are already used to identify a fetus’s gender, blood type, and even any chromosomal or genetic abnormalities.
When certain anomalies that later proved to be cancer in the mother were found, the use of these tests by pregnant women raised the possibility of using cell-free DNA blood testing to identify cancer.
Creation of the Gallieri test
The search began for a blood test that could be used to screen for more forms of cancer using cell-free DNA.
The Food and Drug Administration (FDA) awarded the Gallieri test, which examined the methylation of cell-free DNA in the blood, a Breakthrough Device designation in 2019 after the firm GRAIL spent several years developing it.
The business, working with the National Health Service (NHS) in the UK, announced intentions to begin the PATHFINDER study in February 2020 to assess the effect the test had on the time to diagnosis for cancer patients.
The business aims to finish the study in 2026, with intermediate findings anticipated in 2024, and there are already over 140,000 participants.
At the European Society for Medical Oncology (ESMO) Congress 2022 in Paris, France, this past week, the business made certain findings from the PATHFINDER study’s 6,662 participants public.
Machine learning has been used to evaluate the methylation of cell-free DNA present in blood samples as part of the development of the Galleri test in order to find patterns linked to cancer and even identify the organ or tissue from which cancer originates.
The test operates by sequencing the methylation at each and every DNA base throughout the complete genome. In order to establish whether there is malignant DNA present and where it originates, the data discovered is next examined using machine learning-produced algorithms.
To determine if the Gallieri test expedites cancer diagnosis, the PATHFINDER study was created. Blood testing identified 92 participants with cancer in the sample of 6,662 persons over 50, and 35 patients subsequently received confirmation of 11 different forms of cancer.
When malignancies were identified, over half (48%) were in an early stage, either stage I or II. The majority (about 71%) of cancers were those for which there aren’t any screening programs at the moment, such as liver, small intestine, uterine, pancreas, bone, head, and neck cancers.
In addition to lung and ovarian cancers, Hodgkin and non-Hodgkin lymphomas, oropharyngeal, intrahepatic bile duct, plasma cell myeloma, and plasma cell diseases were also shown to be malignancies.
The majority of the people whose cancer was discovered by the test performed imaging techniques, such as scans or MRIs, to confirm their cancer diagnosis. In addition, 30% of individuals who had false-positive findings underwent more invasive procedures like biopsies to confirm their disease, along with those who received real cancer diagnoses.
The time it took to prove a lack of malignancy after a false positive result was longer than after a real positive result is important to note.
The test diagnosed very few tumors incorrectly, with a false negative incidence of fewer than 1%. This indicates that 99.5% of tumors were discovered using the Galleri test.