No markers appeared in normal DNA from the patient's blood. That shows, Sidransky says, that the clonal markers do in fact reveal the cancer. At least, we think so. We ourselves have shown that in bladder, and we've shown it in brain. Once a cancer acquires a mutation, it doesn't lose it, because that gives it the growth advantage that it needs.
Early evidence indicates that the absence of clonal cells predicts survival for any cancer patient.
The doctors then know how to proceed. Another may need an immediate re-operation to deal with a spot of trouble. For a third, the probe may reveal so many invasive areas that all-out aggressive chemotherapy is indicated. If you pass the Ross Research Building some evening, look up at the 8th floor. Chances are, you'll see the lights on in Sidransky's lab.