New ultrasensitive techniques make this kind of testing possible, and may save patients the pain and anxiety of biopsies and CT scans. It also allows oncologists to more closely monitor whether treatments are working and to change or discard treatment plans if necessary. The blood test is also useful for early diagnosis, as it can detect the presence of cancer DNA before a visible tumor develops, and for follow-up to determine whether cancer is still present after a course of treatment.
It’s still early days, though, for the liquid biopsy—there have been only small studies for some diseases, such as lung, colon, and blood cancers. In one lymphoma study, the test predicted a recurrence more than three months before it was visible on a scan. For lung cancer patient MarySusan Sabini, the test showed that a new experimental drug was working long before the CT scan and X-ray confirmed that the tumors were shrinking.
“Every cancer has a mutation that can be followed with this method,” Dr. David Hyman, the Sloan Kettering oncologist leading the study of the drug Ms. Sabini is taking, told The Times. “It is like bar coding the cancer in the blood.”
The test also can help predict which patients might respond to treatment—for example, some Stage 2 colon cancer patients need both surgery and chemotherapy, and some need the surgery and not the chemo. But as it’s difficult to predict ahead of time, patients may be undergoing treatments they don’t ultimately need. The blood test may be able to determine which patients will still require chemo post-surgery and which ones may be able to skip it.
Some information may not be welcome. The test may also be able to predict which patients aren’t likely to respond to treatment, for example, or identify which patients are likely to have a high risk of recurrence. And some cancers resolve by themselves—and without this sensitive early test, the patient might never have known and so been spared the distress of a cancer diagnosis.
But anything that reduces painful procedures and the brutal side effects of conventional treatments should come as welcome news to cancer patients. Stay tuned for a new study out of Australia, which seeks to predict which patients will need chemo and which won’t.