There is, in principle, only one method for early detection of cancer: regular check-ups. These are often unpleasant, e.g. mammograms or colonoscopies. Plus they are not always 100 % reliable. Wrong diagnoses happen all the time. On the one hand, tumors are occasionally not detected in some people. While on the other, some receive long-term and unpleasant cancer therapies, even though they may never have had cancer in the first place.

Researchers from the European Society for Medical Oncology in Lugano, Switzerland, have now developed a blood test that can accurately detect more than 50 types of cancer. The test can also show where the cancer originated in the body. In many cases before the patient shows the first symptoms.

Less false positive results

In their study ‘Circulating Cell-free Genome Atlas’ (CCGA), the scientists recorded a false positive cancer detection rate of 0. 7%. This means that almost 1% of individuals would be falsely identified as having cancer. Under current methods, about 10% of women are wrongly diagnosed with a false positive cancer when screened for breast cancer. This new blood test was also able to pinpoint the tissue where the cancer originated in 96% of the samples. And it was extremely accurate in 93% of the cases.

Analysis of chemical changes to DNA

The test is predicated on how tumors spread DNA in the blood. This leads to what is referred to as cell-free DNA (cfDNA). However, since this cfDNA can also originate from other cell types, it is often difficult to determine which cfDNA stems from tumours. The Swiss researchers’ blood tests analyse chemical changes in the DNA. This process is known as ‘methylation’, which normally regulates gene expression. “Abnormal methylation patterns and the resultant changes in gene expression can contribute to tumor growth. Therefore, these signals in cfDNA have the potential to detect and locate cancer,” the study explains. This was published in the leading cancer journal Annals of Oncology.

For the test, the researchers examined blood samples from 6689 participants. These were made up of people with pre-existing untreated cancer (2482 patients) and a cancer-free control group (4207 participants). The results from 4316 participants were made available for analysis. 3052 in the training set (1531 with cancer, 1521 without cancer) and 1264 in the validation set (654 with cancer and 610 without cancer).

 

Cell-free DNA is isolated from blood samples from a cancer-free patient (top) or who has cancer (bottom) and subjected to a test. The results, which show methylated (red) or unmethylated (blue) CpG regions, are entered into a ”machine learning classifier” that can identify the presence or absence of cancer and the tissue of origin (TOO) © ESMO

Varying results

The result showed that in most cases the blood test could distinguish between cancer patients and healthy participants. However, discrepancies were observed in the results, depending on the type and stage of the cancer. For example, the percentage for stage I tumors was only 18 %. For stage IV tumours it was 93 %. The average percentage for all 50 types of cancer studied was 43.9 %. For the most common and lethal cancers (anal, bladder, colon, oesophagus, stomach, head and neck, liver and bile tract cancer, lung, ovarian and pancreatic cancer, lymphoma and leukaemia), the percentage was 67.3%.

Potentially suitable for population screening

Despite the somewhat mixed results for very early stages of cancer, the researchers were nevertheless pleased. “These data demonstrate the capabilities of this targeted methylation test. We believe it meets the basic requirements of a blood test for early detection of cancer. The test might be suitable for population screening. You can now detect multiple deadly cancers with a single test,” said the lead author of the article, Dr. Michael Seiden (MD, PhD), president of American Oncology (Texas, USA). “Especially because of its low false positive results and ability to detect where the cancer is in the body.”

“Groundbreaking research”

The editor-in-chief of Annals of Oncology, Professor Fabrice André, Director of Research at the Institut Gustave Roussy, Villejuif, France, also sang the praises of the findings. “This research is groundbreaking. It is a first step towards the development of easy-to-use screening tools. Early detection of more than 50% of cancers could save millions of lives worldwide every year. As well as drastically reduce the morbidity levels arising from aggressive treatments.”

Further research is needed in order to assess to what extent the new blood test can actually detect tumours sooner than conventional screening tests.

Read more IO articles on the subject of cancer here.