An experimental blood test that is sensitive enough to detect a single cancer cell among billions of healthy cells is moving closer to mass production. As my mom is a colon cancer survivor, this news is of particular interest to me. She currently has a colonoscopy every 2 years, and a carcinoembryonic antigen (CEA) blood test which is used to detect colon cancer recurrence. However, not all colon cancer tumors that reoccur will produce this antigen, and those that do may be in later stages when they are more difficult to treat.
Many doctors believe that stray cancer cells in the blood mean that a tumor has spread or is likely to spread, but a test that has the ability to identify such cells has the potential to transform the care for many cancer patients.
Already, researchers have been surprised to learn that more cancer patients have these stray cells than they had originally believed. One study found that a significant number of men with cancer thought to be confined to the prostate had stray cancer cells in the blood. This may be indication that cancer cells are entering the blood soon after a tumor develops, or that the cancer has already spread, but cannot be detected by the methods we have currently been using.
The bottom line is physical examination, tumor markers tests and medical procedures such as CT scan have brought us a long way in the battle with cancer, but it could not hurt to have another test in our arsenal.