A Blood Test To Detect Tumors Could Save Lung Cancer Patients

Liquid biopsies are a potentially breakthrough technology for cancer diagnosis, but still need more work

Photo Illustration: Vocativ
Apr 26, 2017 at 1:00 PM ET

Today, doctors diagnose solid tumor cancers, like those that affect the breast and brain, by testing a small tissue sample in the lab. That can be invasive and takes time to get results.

But what if diagnosis only required a quick blood test? That’s the promise of the growing attention around liquid biopsies, a technique designed to detect individual cancer cells or bits of cancerous DNA floating in patients’ blood, diagnosing cancer more rapidly. However, despite significant investment, experts still aren’t sure the technology works as reliably it should.

A new study indicates that liquid biopsies may be moving in the right direction—repeated tests were able to track the evolution of lung cancer in 100 patients and determine which treatments worked best for them.

To treat a virulent type of lung cancer called metastatic non-small cell lung cancer, patients have to undergo surgery to remove the tumor. Some are given chemotherapy after the surgery to kill the remaining cancer cells, but sometimes those interventions aren’t effective, and the cancer comes back. Previous studies have found that identifying DNA in patients’ blood can predict the relapse of breast and colorectal cancers. And since lung cancer is the leading cause of cancer death, it made sense to see if the same could hold true for it.

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In the study, published Wednesday in Nature, the researchers started with 100 patients diagnosed with lung cancer through traditional methods. They took liquid biopsies of these patients, and did so after surgery, in the next stage of treatment, and in some cases after death.

The results of the liquid biopsies indicated which patients would be resistant to the post-surgical chemotherapy and, in a few cases, predicted the cancer’s resurgence before standard imaging techniques. According to these findings, liquid biopsies might be a critical tool to help doctors best treat this type of lung cancer.

There are still some limitations to liquid biopsies. One is the high cost—it ran the researchers about $1,750 per patient to take the five samples in this study. Another is the sensitivity of the test. Though liquid biopsies are great for detecting large tumors, they couldn’t detect tumors as small as those visible in CT scans, which is more helpful to clinicians as they can start to treat small tumors the cancer earlier.

The technique still hasn’t been validated to make the initial cancer diagnosis, and though the conclusions of this study are promising, liquid biopsies still need further evaluation before they become standard clinical tools.