A blood test that distinguishes tumor DNA from altered non-tumor DNA detected cancer-related mutations in more than half of patients with early-stage malignancies, an worldwide research team reported.
The doctors identified more than three-quarters of colorectal cancer patients, two-thirds of ovarian cancer patients, and most of the lung and breast cancer patients, who exhibited detectable alterations in driver genes.
Proposed use of circulating cell-free (cf) DNA as a diagnostic strategy dates back several decades, but only recently did the technology emerge to permit identification of abnormalities in cfDNA in patients, the authors continued.
The test is a long way from being used to screen for cancer, but the study shows a way to get there, the team reported in the journal Science Translational Medicine.
"There is a lot of excitement about liquid biopsies, but most of that has been in late-stage cancer or in individuals where you already know what to look for, ' lead author Dr Victor Velculescu told the Daily Mail". Further studies still need to be done to replicate the results across larger numbers of people, but the proof-of-concept is a promising step forward in finding a simple, non-invasive way to identify early-stage cancers, and potentially offer beneficial treatment before the tumors grow too large.
This new test's strength is its ability to identify very early-stage cancers at a point when patients would most likely not be displaying any other symptoms. But the main target of this test is to detect cancer as quickly as possible and researchers are quite optimistic about the quick result of the test.
The researchers believe that this test is first of its kind blood test which could effectively recognize cancer inside an individual before even doing any diagnosis.
Dr Velculescu explained it's easy to find mutations if you are looking for something specific.
"The challenge was to develop a blood test that could predict the probable presence of cancer without knowing the genetic mutations present in a person's tumor", says Velculescu.
Velculescu's team developed an approach called targeted error correction sequencing (TEC-Seq for short).
The approach examined 58 cancer-related genes through deep sequencing DNA 30,000 times over to look for mutations in the DNA of tumor cells that float in the body. The test was more accurate in later-stage cancers. In the colorectal cancer subgroup, patients with stage IV disease had a significantly higher cfDNA concentration compared with patients who had stages I-III cancer (66 versus 21 ng/mL, P=0.006).
Among 45 breast cancer patients, the test spotted cancer-derived mutations in 67% patients with stage I disease, 59% with stage II disease and 46%with stage III cancers.
While that's good, it's not a great result. They also sequenced mutations in tumors from 100 of the patients studied, and found that in 82 patients, the same mutations found in the blood corresponded with those found in the tumor tissue. The first goal would be to try it in people at high risk of cancer but no symptoms yet - such as smokers, or people with cancer-causing gene mutations like BRCA mutations, Velculescu said.
Velculescu said the next steps for the test will be to expand the investigation to include more patients, and with different tumor types, and to conduct clinical trials to determine the impact of early detection on clinical outcomes.
Overall, the scientists were able to detect 86 of 138 (62 percent) stage I and II cancers.
For 42 patients with ovarian cancer, 67% with stage I disease were correctly identified, as well as 75% with stage II disease, 75% with stage III cancer and 83% with stage IV disease.