Tumor DNA in blood and bile: a shortcut to understanding bile duct cancer

The problem

Today, some patients with biliary tract cancer (cholangiocarcinoma and gallbladder cancer) can receive drugs that target specific genetic changes in the tumor, and this has improved survival. To find these changes, however, the tumor has to be tested. The bile ducts are hard to reach, and a biopsy often yields little material or has to be repeated.

The alternative

Tumors shed small fragments of their DNA into the blood and, in the case of the bile ducts, into the bile as well. Analyzing this material, known as circulating tumor DNA, makes it possible to study the tumor's genetic profile without another biopsy. In this review, we brought together what studies show about this approach.

What the review shows

• Blood agrees well with tissue in most cases, especially before any treatment and when there are metastases.
• Bile is an even more reliable source than blood for finding the tumor's genetic changes.
• Tracking tumor DNA during treatment shows whether the tumor is responding and when it starts to become resistant. When tumor DNA disappears from the blood, this usually goes hand in hand with disease control.
• Detecting the return of the disease before it shows up on imaging is possible in early studies, but it is still being researched.

What this means for you

When a biopsy is not enough or is risky, testing tumor DNA in the blood, or in the bile, may be the way to identify changes that have a targeted treatment. It is a conversation worth having with your oncologist from the time of diagnosis.

The limitations

The studies are still small, tests vary between laboratories and the cost is high. So routine use to monitor treatment or look for relapse still depends on larger studies.

For information only. It does not replace an individual medical assessment.