Early pancreatic cancer may be caught by a simple blood test
A small preliminary study suggests that a simple blood test based on detection of tiny epigenetic alterations may reveal the earliest signs of pancreatic cancer. The disease is nearly always fatal because it is not usually discovered until it has spread to other parts of the body.
These research findings, if confirmed, could be an important step in reducing mortality from the cancer, which has an overall 5-year survival rate of less than 5% and has seen few improvements in survival over the last three decades.
"We have had nothing to help us screen for pancreatic cancer," said study leader Nita Ahuja, MD, an associate professor of surgery, oncology and urology at the Johns Hopkins University School of Medicine in Baltimore, Maryland. The study was published in Clinical Cancer Research (2013; doi:10.1158/1078-0432.CCR-12-3224). "While far from perfect, we think we have found an early detection marker for pancreatic cancer that may allow us to locate and attack the disease at a much earlier stage than we usually do."
For their study, Ahuja and her colleagues were able to identify two genes, BNC1 and ADAMTS1, which together were detectable in 81% of blood samples from 42 people with early-stage pancreatic cancer, but not in patients without the disease or in patients with a history of pancreatitis, a risk factor for pancreatic cancer. By contrast, the commonly used PSA antigen test for prostate cancer only picks up about 20% of prostate cancers.
The researchers found that pancreatic cancer cells appear to have chemical alterations to BNC1 and ADAMTS1—epigenetic modifications that alter the way the genes function without changing the underlying DNA sequence—that silence the genes and prevent them from making their protein product, the role of which is not well-understood. These alterations are caused by the addition of a methyl group to the DNA.
BNC1 and ADAMTS1 were found in 97% of tissues from early-stage invasive pancreatic cancers. Surgery offers the best chance for survival in pancreatic cancer, because radiation and chemotherapy are not very effective against the disease. Surgery is more likely to be successful when the cancer is smaller, which is when it is detected earlier.
Ahuja explained that the practical value of any blood test for cancer markers depends critically on its sensitivity, meaning the proportion of tumors it detects and its specificity (ie, how many of the positive results are false alarms). This pair of biomarkers has a specificity of 85%.
Ahuja also cautioned that her team still needs to duplicate the results in a larger sample of tumors, but is encouraged by the results so far. She stated that the test is likely to be offered to people who are at high risk for developing the disease, such as those with a family history of pancreatic cancer, a previous case of pancreatitis, long-term smokers, or people with the BRCA gene mutation, which is also linked to breast, ovarian, and pancreatic cancers.