What is the difference between a normal cell and a cancer cell? The answer lies in their DNA. Cancer results from the accumulation of genetic mutations, which trigger uncontrolled cell growth. Cancer’s mutated DNA can reveal its presence early on in the disease. Like leaving fingerprints at a crime scene, tumor cells release small pieces of DNA into the bloodstream. This “circulating tumor DNA” can now be detected via a blood test.

Researchers at the Johns Hopkins Kimmel Cancer Center tested blood samples from 44 healthy individuals and 200 patients with colorectal, breast, lung, or ovarian cancers. Using DNA sequencing techniques, they analyzed changes in 58 known oncogenes and correctly identified tumor-related DNA mutations in 48 of 62 (77%) patients with late-stage cancer (III or IV), and in 86 of 138 (62%) patients with stage I or II cancer. Importantly, none of the cancer-derived mutations were identified in the blood samples from healthy individuals.

Despite these exciting results, the blood test will need to be validated in larger studies before it can be considered for FDA approval. There are also ethical considerations when it comes to detecting very early-stage cancers. Some cancers are not life-threatening, making the side effects of treatment worse than leaving a tumor alone. As detection methods improve, it will become increasingly important to distinguish harmful cancers from those without a long-term impact on survival.

Acknowledgments: Many thanks to Nicholas Warren, a graduate student in the Experimental and Molecular Medicine program at Dartmouth College, for providing his expertise and commentary on the topic.

Managing Correspondent: Benika Pinch

Media Coverage: Blood test shows promise for early-stage cancer detection. Chicago Tribune