Thangamani Seenivasan, MD, Oncology Surgeon, Division Chief of Surgical Oncology, Cancer Liaison at Steeplechase Cancer Center to American College of Surgeons, talks about a new diagnostic test to help detect cancer recurrence.
How do you keep track of a person’s cancer after they’ve gone through treatment?
SEENIVASAN: There are NCI guidelines for almost every cancer we treat. These are guidelines proposed based on the evidence. For colon cancer patients, as soon as their surgery is done, it takes a village to take care of them. Along with the medical oncologist, they have a follow-up three months for first one and then six months for the next two years, then yearly. When I say follow-up, it’s a combination of blood tests, scans, and physical examination and evaluation of the patient thoroughly to identify any evidence of recurrence of disease. So, we do have evidence-based guidelines that we follow.
Why is it so important to monitor and stay on top of what’s going on after a patient is done with treatment?
SEENIVASAN: Unfortunately, even in 2020, we have not enough tools to fight cancer. Based on the current test, we can identify the recurrence after a delay, but it increases our difficulty to treat these patients. So, early detection is still difficult. That’s probably the reason we look forward for evidence-based innovation like Signatera, which is a circulating tumor DNA test.
Tell us about Signatera? What is it and how does it work?
SEENIVASAN: Signatera is a circulating tumor DNA test. The public is more familiar with our sex identification during pregnancy test. If fetal DNA is detected in the mother’s blood, currently, parents want to know the sex of the child. They take a sample of the mother’s blood and can find the DNA of the fetus and know accurately the sex of the child. In the past, we used to use ultrasound scan and other tests.
So, Signatera is a blood test?
SEENIVASAN: That’s correct.
And, it’s looking for the circulating DNA? Is it picking up tumor markers?
SEENIVASAN: Signatera is also called liquid biopsy. Although it’s called a biopsy, it’s not really a biopsy or invasive. The liquid part is probably correct. It’s a blood test if done at the home of the patient, and it’s noninvasive. The tumor DNA, the name for Signatera, when somebody has a tumor and the tumor spread, obviously they’re circulating in their bloodstream. The DNA we identify is a tumor DNA. How do we know that? Because the resected cancer specimen is identified, and we already know the DNA in the tumor. When the blood samples are taken, the DNA that matches the tumor are identified, so we are very accurate in identifying the tumor cells in the blood.
If a patient has this blood test and you see some of that DNA starting to circulate in the blood, would he or she show symptoms? How early could that DNA be circulating before it would be picked up by other tests?
SEENIVASAN: Well, this is the exciting part of the innovation. It’s very early. There are no symptoms and signs, and we are getting early evidence. The tumor cells are identified earlier by a year before patients get symptoms. They are seen in CAT scans and PET scans that we do to identify this early metastasis.
What can you do for a patient if you see that the DNA has evidence of the tumor in it?
SEENIVASAN: I would certainly say this is evolving and the information is valuable and accurate. It lets us talk to patients and inform them that there’s a circulating DNA of the tumor, and there is recurrence evidence seen in the liquid biopsy. We do encourage the patients to have tests earlier than a year. We focus on areas of metastasis and are extra vigilant about it. Do we know everything about it yet? It’s a very early stage, but very promising. We still have information to gather. It’s very valuable if somebody that is circulating DNA has been negative in the previous test and then it appears, then you’re concerned. They start evaluating that patient. Also, it’s very valuable if it has been positive and you have given a treatment and it’s cleared and it’s negative in the subsequent test. That’s very encouraging and there’s good evidence to support that the treatment is working. We continue to treat the patient because the circulating tumor DNA is persistent. It tells us this is not the effective treatment, so maybe we should try a different treatment that may work. Instead of waiting months and years, the physicians get to sit together, evaluate these patients, and discuss how to make it better. This is the area I get most excited about. We don’t have enough tools in cancer care, and this is a very valuable tool, an effective tool. I would love to have innovations like Signatera to come and would love to support and get my patients all the help they need.
How often does a patient have to do the Signatera test? Every three months?
SEENIVASAN: At this moment, currently my patients are having every three months. I would certainly say as we go by, this would change.
If a patient were to show signs of the tumor DNA, there is treatment. Would that indicate patient could get chemotherapy to knock it into remission? Would patient be available to have that treatment right away instead of waiting a year or 18 months?
SEENIVASAN: I would think so. If there’s a circulating DNA tumor seen in the patient, the tumor metastasis risk is high. Currently, there is a patient with stage two colon cancer. We do know that the recurrence rate is low, but it’s not zero. If these patients are evaluated with Signatera, and there’s a negative test, clearly, we know the metastasis chances are not there. But at the same time, another patient has a Signatera test positive, although it’s a stage to the current recommendation of no chemotherapy, that patient still has a potential for developing a recurrent disease. We see more younger and younger patients, and they would benefit from this test and would certainly discuss treatment options. They have a higher risk of recurrence and it’s better to treat them early and improve their quality of life.
Could you walk our viewers through what happens with the test?
SEENIVASAN: Sure, I’m going to give an example. There is a young patient with colon cancer. I do the surgery robotically most of the time and send the specimen to the pathology lab. So, a sample of tissue is sent to Signatera lab to identify the tumor DNA. From there, we coordinate with the innovators and patients to do an immediate blood draw at home. Usually, a nurse will assist them with precautions, especially during the pandemic times. They get the test done and are clearly done three months after that. The turnaround time for the test is about seven to 10 days. We get the information and I coordinate with my multidisciplinary cancer team, which includes medical oncology, genetic counselor, radiation oncology and the radiologist pathologist. We coordinate and analyze this test and the value. We certainly want to learn and want to support evidence-based innovation. We currently don’t have enough treatments to make our patients better. So, this is an exciting product.
Can we talk a little bit about your patient, Scott? He had cancer and has a genetic condition that predisposes him?
SEENIVASAN: Right. Scott is an interesting patient. He was very nervous when he came to see me. He already had a colonoscopy. They found several polyps, cancer, and one cancer area. He has a rare condition called Mutori syndrome, which is a subtype of Lynch syndrome. The important part of it is the rare autosomal dominant disorder and the particular syndrome that he is identified as has a higher risk of multiple colon cancers and genital urinary cancer, which is kidney and bladder and skin cancers of all types. By the time he came to me, he had over 15 skin cancers removed. He was very apprehensive. At the multidisciplinary conference, the current guideline is it’s better to remove all of his colon because we can alter the course of developing colon cancer. He learned a lot and worked with us. He had the surgery right in the middle of Covid-19. We took precautions and he’s done very well. The exciting part is he had a tiny cut, he went home, and he has stage two colon cancer. The standard of care in 2020 is chemotherapy for stage three. Stage two needs surveillance, which is continuous monitoring and evaluation as per NCA guidelines. This fellow is certainly a high-risk patient. He’s going to get a lot of value from the test. We do know that he has no tumor DNA in his blood. So, it’s a valuable test in this case. And, we’re going to monitor him closely and learn and help him a lot.
Is there anything I didn’t ask you, doctor, that you want to make sure people know?
SEENIVASAN: The most important thing is more science is better for the cure. I want the message to be spread to everyone. I think with modern day television, Internet, this message could be spread instantly. So, I’d all the public to know about the Signatera test or any test that’s helpful. Also, I will tell all my patients that prevention is better than cure. We do a lot of wrong things when it comes to colon cancer. We all know there is a limit to the red meat and WHO already says limit processed sausages, and bacon. But, we somehow tend to ignore it. I tell all of my patients to enjoy a small amount. You cannot have it every day. I mean, prevention is better than cure. That’s something I want to tell the public and use every innovation possible. Science is hindered by limitation. I would like to see more science to help us.
Interview conducted by Ivanhoe Broadcast News.
END OF INTERVIEW
This information is intended for additional research purposes only. It is not to be used as a prescription or advice from Ivanhoe Broadcast News, Inc. or any medical professional interviewed. Ivanhoe Broadcast News, Inc. assumes no responsibility for the depth or accuracy of physician statements. Procedures or medicines apply to different people and medical factors; always consult your physician on medical matters.
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