Cancer doesn’t “come back” as much as distant micro-metastases were always there: too small to be detected – until now.
Residual cancer cells can now be tracked by new technology.
Signatera is a personalized cancer monitoring test that uses a patient’s unique genetic information to track the presence of residual cancer DNA that does not show up on imaging scans.
It is these residual or hiding cancer cells that “come back” in a relapse situation after the patient has been given the all-clear and deemed to have no evidence of disease (NED).
“I use Signatera in all of my patients, and feel that it is helpful in the following circumstances,” begins Jonathan Stegall, MD, an integrative oncologist and medical director for The Center for Advanced Medicine, an adult cancer treatment center in Alpharetta, GA.
“At baseline, before starting treatment, to measure the systemic burden of cancer.
“After we have been doing treatment for a specified period of time, as a way to monitor treatment efficacy (I typically recheck after the first month of treatment).
“When imaging shows no evidence of disease, and we want to confirm that (I’ve seen plenty of cases with clear scans but evidence of remaining cancer on Signatera).”
By analyzing blood samples, Signatera can detect tiny amounts of tumor DNA that might remain, helping doctors monitor for potential relapse or disease progression.
A single cancer cell. Cancer.gov/Bruce Wetzel, Harry Schaefer
This test is tailored to each individual based on their specific cancer mutations, making it a highly targeted tool for ongoing cancer management.
“Unfortunately, because it is a blood test, it is not able to tell us where in the body the cancer is,” says Dr. Stegall.
So for instance, a patient is diagnosed with stage 2 melanoma skin cancer – a deep melanoma that, by definition, has not spread beyond the skin.
The tumor on their chest is excised, and a generous margin of seemingly healthy tissue around it is also removed.
The patient requests a chest MRI scan (this procedure is not standard protocol for stage 2 melanoma) since the lungs are a favored metastatic site for melanoma.
The MRI results are negative.
However, in this patient’s lungs is microscopic metastatic melanoma that the sensitive MRI was not able to see.
The Signatera blood test for this particular patient would indicate that melanoma DNA is present somewhere other than the skin but without revealing the location (lungs).
“However, based on the tissue analysis done upfront (when we first order Signatera), we do know that what we are measuring in the blood is specific to each patient and his or her cancer,” says Dr. Stegall.
“The unique molecular pattern they identify is set in stone, and does not change with time OR as a result of treatment.
“While these cancer genetic fragments in the blood don’t tell us with 100% certainty that cancer has set up shop somewhere new, it does tell us that cancer has the potential to (since we know that the two main ways cancer spreads are through blood and lymph).”
So in the case of the melanoma patient, Signatera would be accurate in terms of detecting melanoma DNA somewhere other than the skin.
But a positive Signatera result in a given patient doesn’t always mean that there’s a missed metastasis beyond the primary site of the original cancer.
In short, a negative Signatera result is very reassuring, but a positive one warrants further investigation such as additional scanning.
“It also tells us about cancer activity, since these fragments are spilled into the blood when a cancer cell divides into two cells,” continues Dr. Stegall.
“I will typically recommend treatment in these instances, although there is no consensus on this yet.
“Some doctors might choose to wait until evidence shows up on more conventional testing, such as imaging, before recommending treatment.
“My question to them, is, ‘Then why are you ordering Signatera testing if it doesn’t change your management of the patient?’
“Since Signatera also doesn’t measure any other types of cancer, but only the one they have been diagnosed with, I also frequently employ Galleri testing for patients who consistently have no evidence of disease on routine labs, imaging and on Signatera testing.
“Galleri is a screening test that is designed to look for over 50 types of cancer in the body.
“It is not diagnostic, but if it gets a cancer signal, it claims to be able to predict with fairly high certainty what the site of origin/cancer type it is.
“Their hope is that this will one day be covered by insurance, so that it will become a routine test ordered by primary care providers, with the goal of detecting more cancers at earlier stages.”
Jonathan Stegall, MD,
