The individual fates of the 1.3 million Americans diagnosed with cancer this year will be largely decided by one simple factor: at what stage was the disease spotted?
Ovarian cancer offers a fearsome example. Because of its vague symptoms, it is usually ignored or misdiagnosed, sometimes for years. Eighty percent of patients don’t find out they have it until it’s spread beyond the ovaries. At that point, it is usually incurable; only one patient in three survives five years after diagnosis. On the other hand, surgery can cure 90 percent of patients whose cancer is detected while still confined to the ovary. Even notoriously lethal cancers of the lung and pancreas are anything but a death sentence, if caught early enough. “Cancers can almost always be cured by simple, classical surgical techniques, if they’re detected early,” says Bert Vogelstein, a molecular geneticist at the Howard Hughes Medical Institute at Johns Hopkins.
The problem, of course, is that cancers, which begin with just a few deviant cells, are by their very nature hard to diagnose early. In the last few years, though, a new method has emerged that promises to deliver simple blood tests that identify the telltale molecular profiles of various cancers easily and accurately. It has long been known that cancer leaves traces in the blood, but these hints are confusing and ambiguous. “Blood is perfusing through every tissue in your body, 60 times a second, beating through it,” says National Institutes of Health pathologist Lance Liotta. “You’d imagine there’d be fragments of what’s going on in every cell, and every tissue, ending up in the circulation.”