Scientists have developed a noninvasive, feasible and safe method to detect tumour cells in the pancreas and bile ducts, which could lead to early diagnosis for pancreatic cancer.
By collecting samples from the portal vein - which carries blood from the gastrointestinal tract, including from the pancreas, to the liver - physicians can learn far more about a patient's pancreatic cancer than by relying on peripheral blood from a more easily accessed vein in the arm, researchers from the University of Chicago in US have found.
Primary tumours shed cancerous cells, known as circulating tumour cells (CTCs), into the blood. These have been widely studied as prognostic biomarkers for various cancers.
Since these cells are often larger, irregularly shaped and tend to cluster together, they get trapped in smaller vessels.
The researchers hypothesised that most cells released from a gastrointestinal tumour would flow into the portal vein and then get sequestered by the narrow vessels in the liver.
These cells would not reach the peripheral venous system. CTCs from gastrointestinal tumours are rarely identified in the peripheral blood until the cancer is widely metastatic.
To test this theory, researchers used an ultrasound-guided endoscope and a small needle to take blood from the portal vein during routine diagnostic endoscopies.
They found CTCs in 100 per cent of 18 patients with suspected tumours in the pancreas and bile ducts. Tests using peripheral blood samples, the standard method, detected tumours cells in only 4 of the 18 patients.
"We demonstrated that this method is potentially quite valuable as well as noninvasive, feasible and safe," said study director Irving Waxman, professor of medicine and surgery and director of the Centre for Endoscopic Research and Therapeutics at the university.
"We had no complications related to portal vein blood acquisition," said Waxman.
Only seven per cent of patients diagnosed with stage II disease are still alive five years after diagnosis, making it one of the most lethal forms of cancer, the researchers said.
The portal vein samples contained far more tumour cells in all stages evaluated, including locally advanced as well as metastatic tumours, the researchers said.
Blood collected from the portal vein had a mean of more than 100 CTCs per 7.5 millilitres. Patients with less advanced disease, who could potentially benefit from surgery to remove the tumour, had fewer CTCs. Those patients averaged about 80 CTCs per 7.5 millilitres.
In contrast, when the researchers used peripheral blood to test the same patients, they found few, if any, circulating tumour cells.
Those samples contained less than one CTC in 7.5 millilitres of blood, the equivalent of one cell in a billion.
The study was published in the journal Gastroenterology.