DNA mutations enable detection of early-stage cancers with a blood test
Scientists are one step closer to developing a functional blood test to detect a range of cancers. By identifying specific cancer DNA mutations, researchers at the Johns Hopkins Kimmel Cancer Center are reporting success in detecting the presence of early-stage cancers in blood samples.
Previous research in identifying mutated DNA signposts for cancer has relied on looking at biopsied tumors from individual patients. The genetic mutations found in the tumor samples offer doctors solid signposts that can then be traced back to a patient's blood sample, but these DNA markers are often highly specific to the patient and not broadly applicable in a more general blood test.
"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 professor of oncology at Johns Hopkins Kimmel Cancer Center, Victor Velculescu, M.D., Ph.D.
In developing this new test the team started out by focusing on 58 genes that are already known to be widely linked to specific cancers. They then studied blood samples from 200 patients with breast, lung, ovarian and colorectal cancer.
Using a type of genomic sequencing called "targeted error correction sequencing", the team was able to accurately identify mutations in the targeted genes. This method proved successful in detecting the presence of cancer in 62 percent of patients with either stage 1 or stage 2 cancers.
The technique was most successful in identifying colorectal cancers, correctly finding the presence of cancer in 35 out of 42 previously diagnosed patients. Accuracy increased for patients with more progressed stage 3 and 4 cancers.
Importantly, the experiments also examined blood samples from 44 healthy individuals and found no presence of these cancer-signaling genetic mutations. which reduces the potential for the test to deliver false positives.
A big challenge the researchers now face is trying to refine the number of DNA locations screened while still preserving the test's accuracy. This kind of genetic sequencing is not cheap, but Professor Velculescu is confident that it is becoming more cost-effective.
Several different cancer detection blood tests are currently in development around the world and each has its own novel detection method. RNA blood platelet profiles, DNA damage in white blood cells and elevated levels of a specific protein, are all strong targets currently being investigated by researchers.
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. 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.
The study was published in the journal Science Translational Medicine.