New blood test can help detect cancer early
Cancer blood test hero
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By Smartencyclopedia Newsroom with Deutsche Welle*

By the time the diagnosis was made, it was already too late as the cancer had extensively spread from the patient’s pancreas to nearby organs. Surgical intervention was no longer a viable option. Tragically, just four months later, at the tender age of 31, the young German man succumbed to the disease.

Despite advancements in cancer treatment in recent years, therapy often falls short due to the late detection of tumors. Symptoms such as stomach pain or fatigue, particularly in the early stages, can be vague, leading patients to seek medical attention only when the disease has become difficult or even impossible to treat.

However, a breakthrough blood test called Galleri aims to change this narrative. Developed by the American healthcare company Grail, the test has the potential to identify over 50 different types of cancer through a simple blood sample. Recently, scientists presented the results of a Galleri study at the renowned American Society of Clinical Oncology (ASCO) annual meeting, the world’s largest cancer conference.

The research team, led by the University of Oxford scientists, employed the Galleri test on over 5,400 patients displaying symptoms suggestive of cancer. Prior to undergoing standard diagnostic examinations, the patients also provided a blood sample for the assessment using the Galleri test. Remarkably, in two out of three patients who were ultimately diagnosed with cancer through conventional diagnostic methods, the blood test successfully detected a cancer signal as well.

However, it is important to note that the test also yielded false positive results, indicating that 79 participants had cancer when they were actually cancer-free. These false positives present a challenge as they can mistakenly label healthy individuals as patients, potentially causing unnecessary distress and medical interventions.

Mark Middleton, the lead researcher of the study, acknowledged the potential issues associated with false positives. In an interview with DW, he expressed concerns about incorrectly tagging healthy individuals with a label that inaccurately suggests they have cancer.

This situation can be highly stressful for both patients and healthcare professionals, carrying emotional and economic burdens.

Despite these challenges, the potential of the Galleri test to facilitate faster testing and potentially improve therapy is generating significant excitement among researchers and clinicians. Early detection of cancer significantly improves survival rates compared to later-stage diagnoses when the disease has already spread.

One of the notable advantages of the Galleri test is its ability to detect over 50 different types of cancers, including those that are typically diagnosed at advanced stages with low survival rates, such as ovarian or pancreatic cancer. The test also covers cancers that currently lack routine screening methods, expanding the possibilities for early detection and intervention.

The Galleri test operates by detecting fragments of tumor DNA in the bloodstream. When a cell dies, its DNA is released into the blood, and the DNA of cancer cells carries distinct markers that differentiate it from healthy cells. Specifically, cancer DNA exhibits a specific pattern of methylation, which is a chemical modification of DNA.

Niels Halama, an expert from the German Cancer Research Center who was not involved in the Galleri study, explained that these patterns of methylation are typically found only in cancers. The Galleri test is designed to identify and analyze these patterns.

Since the pattern of methylation can vary depending on the type of cell, the Galleri test can also provide information about the origin of cancerous cells in the body. The researchers in the study were able to determine the location of the tumor in 85% of cases using the test results.

This aspect of the test is particularly valuable as it aids in determining the appropriate follow-up tests and examinations. For instance, if the Galleri test indicates pancreatic cancer, clinicians can promptly conduct specific tests for pancreatic cancer to confirm the diagnosis. This targeted approach saves crucial time and resources by avoiding unnecessary investigations for other diseases.

However, scientists are cautious in declaring the Galleri test a breakthrough at this stage. Unlike conventional tests that rely on specific thresholds to indicate the presence or absence of a particular condition, the Galleri test functions as a pattern decoder. It analyzes the unique methylation patterns associated with cancer rather than providing a binary result. Ongoing research and refinement of the test are still necessary to fully understand its potential and limitations.

Niels Halama, an expert in the field, drew an analogy to explain the intricacies of the Galleri test. He compared it to looking at different pictures and being able to identify the Mona Lisa based on its unique features while recognizing that other paintings, such as those by Vermeer, are distinct from the Mona Lisa. However, he emphasized that there are variations and nuances in between, making the interpretation more complex.

Currently, the Galleri test functions as a learning machine, continuously improving with each new sample it analyzes. This iterative process is a source of optimism for the researchers involved.

However, there are certain limitations and considerations to be aware of. Presently, the strength of the test lies in its ability to prompt further testing at an early stage rather than providing a definitive diagnosis of cancer. A positive result indicates the need for additional tests to identify the presence of cancer.

One current limitation is the requirement for a sufficient amount of genetic material in the bloodstream for the test to detect tumor cells. If a tumor is not producing an adequate amount of genetic material, it may go undetected by the test.

Additionally, the Galleri test cannot detect all types of cancers due to the absence of specific markers required for detection. Some tumors may lack these markers, rendering them undetectable through this particular test.

Halama noted that such tumors are unlikely to ever be detectable using this type of test.

It’s important to note that the study discussed in the article only included patients who were already exhibiting symptoms. The test demonstrated higher accuracy in older patients, those with advanced cancers, and those with upper gastrointestinal tumors. Future studies will need to evaluate the test’s performance in patients without symptoms, less advanced cancers, and cancers located outside the gastrointestinal tract.

Currently, scientists are conducting a study with 140,000 participants in the UK to assess the potential of the Galleri test as a general health screening tool. The results of this study are expected to be available later this year and will shed further light on the test’s capabilities and implications.

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