Doctors say a new treatment is proving to be a game-changer for some patients with tumor-based cancers.
It’s a simple blood test that shows the recurrence of cancer months before it can appear on traditional scans like MRIs, CT scans and X-rays by looking for cancer cells in the patient’s blood.
The so-called circulating tumor DNA test (ctDNA), sold under the name Signatera, is now being used to check for leftover cancer cells after the initial cancer surgery, to monitor whether cancerous cells and tumors have returned and to assess whether a patient is responding to cancer treatment.
Dr. Georges Azzi, an oncologist at Holy Cross Hospital in Florida, has been using the test on some of his patients. The test is only for patients with tumor-based cancers because the tumor provides a specific DNA barcode that the blood test can pick up on.
“If the test is positive, it is with 99.9% confidence that the tumor is back,” he says. “There could be nothing else that could cause that positive result.”
For stage 2 colorectal cancer, for example, negative tests within 30-days post surgery have 88% confidence that the tumor will not return, Azzi says. If the cancer patient maintains a negative ctDNA test throughout the first year, the risk drops to less than 3%, he says. This helps determine which patients are at high or low risk of recurrence.
Before the ctDNA test, cancer patients were treated in the same way. But now, he says studies are testing whether patients with negative ctDNA tests can safely skip chemotherapy. Preliminary data looks hopeful, he says, but he’s waiting for the official confirmation.
One of Azzi’s patients, Bonnie Miller of Washington state, was diagnosed with bladder cancer in 2018 before the ctDNA test was available.
She began the testing as she was enduring many side effects due to immunotherapy treatment. During a bladder cancer recurrence, her doctors used the ctDNA test and found that her cancer was not responding to treatment. This enabled them to quickly switch to a different treatment.
After trying a new treatment, the test showed that her cancer was responding well, and eventually, allowed her to safely stop the treatments.
Now Miller uses ctDNA tests to monitor for cancer cells, and so far, it’s found none. The noninvasive test has allowed her to live life fully again, she says.
“One of the best things with the Signatera was that it was a personalized approach. They took my tumor sample, analyzed it and then developed this test specifically to my tumor,” she says. “It gave me peace of mind. Getting the results of that made me feel comfortable in enjoying life.”
On what the ctDNA test can be used for
Azzi: “It is not a screening test. So we should still stick to our regular screening tests. But this helps us monitor the patient on their journey after a cancer diagnosis.”
“... This test can apply to all kinds of cancers — lung bladder, breast, all kinds of tumor in the body except for brain cancers. And the most recent use of this test was immunotherapy monitoring.”
On how the ctDNA test is helpful during immunotherapy treatments
Azzi: “So this test actually is a quantitative test, so it tells you the amount of tumor there is. So in the immunotherapy setting, we obtained this test prior to starting the treatment and after six weeks of starting treatment and if the quantity of the result goes down, it indicates a good response to therapy prior to even being able to perceive any difference on imaging, because imaging will take two to three months to show that difference. So it can tell you from the get go if the patient will respond or not.”
On Miller finding out she was tumor-free
Miller: “I can kind of resume some normal activities. And we're doing now a three-week vacation that we haven't been able to do for three and a half years. And I'm optimistic that there can be a future. When you get the first diagnosis that you have cancer, your question is, ‘am I going to die?’ It produces an anxiety in you and you start worrying about all these little things and you do have a tremendous amount of side effects.”
On her advice to other cancer patients
Miller: “There is an optimistic way to look at getting the blood test. The first thing is it's not going to hurt you to donate blood, but it's going to be protective. And I think they ought to look at it in that light that it can indicate that, yes, their cancer is declining in growth, not spreading. It can indicate, yes, the disease is still progressing and you need to look at alternate routes of treatment. Like mine had metastasized to the lymph nodes and that's one of the areas that's difficult to always discern. You get a brain scan, a chest scan and abdomen scan, and it's a relief to have this test.”
This segment aired on June 14, 2021.