Circulating tumor cells can be detected several months, and even several years in some cases, before the cancer becomes detectable on computed tomography (CT), according to new research. This warning information could play a key role in early surgical intervention, thereby making it possible to attempt the early eradication of the primary cancer site.

Studies carried out in animals have clearly shown that invasive tumors shed cancer cells into the bloodstream from the very earliest stages of their formation, even before the tumors are detectable by diagnostic imaging. The possibility of identifying these sentinel cells is considered a major asset in the race against time for the early detection, and hence treatment, of cancer. Circulating cancer cells are extremely rare in the bloodstream, are very heterogeneous and fragile, and are difficult to isolate without bias or loss.

The team of researchers, led by Paul Hofman, MD, PhD, of Inserm Unit 1081 and the University of Nice in Nice, France, used a blood test that isolates all types of tumor cells from the bloodstream, without any loss, and leaves them intact. The team studied a group of 245 people without cancer, including 168 patients at risk of later developing lung cancer because they had chronic obstructive pulmonary disease (COPD). The study was published in PLoS One (2014; doi:10.1371/journal.pone.0111597).

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Participants systematically underwent the blood test and standard diagnostic imaging tests. Using the blood test, circulating cancer cells were identified in five patients (3%), whereas imaging did not show any nodules in the lungs.

In these five patients, a nodule became detectable 1 to 4 years after the circulating cancer cells were detected by the blood test. They immediately underwent surgery, and analysis of the nodule confirmed the diagnosis of lung cancer.

Monitoring patients for a minimum of 1 year after surgery showed no sign of recurrence in the five patients, leading to hope that the cancer had been eradicated. At the same time, no nodules were detected while monitoring in subjects who did not have circulating cancer cells, and no cancer cells were detected in the bloodstream of control subjects without COPD.

Lung cancer is one of the most lethal cancers. According to the American Cancer Society, 1-year survival among these patients is 44%, and 5-year survival only 16%. Only 15% of these cancers are presently diagnosed at a stage where the disease is localized. Early detection could both improve patient survival and help to improve health economics. COPD is the third leading cause of deaths in the United States, and is mainly caused by smoking.