PET/MRI biomarkers guide personalized treatment for people with pancreatic cancer, study finds
By Ethan Grove
Positron emission tomography (PET)/MRI has changed how Mayo Clinic specialists treat patients with pancreatic cancer.
A positron emission tomography (PET) scan is an imaging test that can help reveal the metabolic or biochemical function of tissues and organs. The PET scan uses a radioactive drug, or tracer, to show both normal and abnormal metabolic activity. A PET scan can often detect the abnormal metabolism of the tracer in diseases before the disease shows up on other imaging tests, such as computerized tomography (CT) and magnetic resonance imaging (MRI). PET images are typically combined with CT or MRI.
Mayo Clinic pioneered the use of PET/MRI to manage pancreatic cancer. A recent study by Ananya Panda, M.B.B.S., a Mayo Clinic neuroradiology resident, and colleagues systematically evaluates the strengths of PET/MRI for pancreatic ductal adenocarcinoma, the most common type of pancreatic cancer.
In less than five years, Mayo's PET/MRI practice has grown from a brand-new technology with unknown promise to the most important imaging available to treat pancreatic cancer.
Mayo added its first PET/MRI scanner in 2015 in Rochester, with additional scanners added in Arizona in 2016 and Florida in 2017. Pancreatic cancer imaging has been one of the primary drivers behind significant growth in PET/MRI.
"It has revolutionized what we do," says Mark Truty, M.D., a hepatobiliary and pancreatic surgeon at Mayo Clinic. "The PET/MRI has advantages over a regular PET/CT scan because it combines both a higher-sensitivity PET scanner with a high-resolution MRI, and they do it at the same time. So you could see all the anatomy, along with the tumor and how much of the tumor is alive." Dr. Truty is a co-author on the study.
During a conference presentation, Dr. Truty had an aha moment. "I heard the presenters talking about PET/MRI, and I said: 'Wait a second, that's exactly what I have been looking for in caring for patients with pancreatic cancer. Let's use it.' And now the No. 1 indication for PET/MRI at Mayo Clinic is pancreas cancer."
Dr. Truty, a world-renowned surgeon who specializes in pancreatic cancer care, says surgery offers patients the best chance at a longer life. But these operations are more likely to succeed after chemotherapy. PET/MRI helps the team know whether the current chemotherapy regimen is working or if another is needed, and when there is enough dead tumor tissue for a surgery to be effective.
"We can see the tumor die on the PET/MRI scan images," Dr. Truty says. "From the patient perspective, if you're going to get chemotherapy that has side effects, you better be sure it's doing what we think it's doing. And that's what the PET scan allows us to determine much better than a regular CT scan."
PET/MRI images then indicate when surgery can be performed to the greatest effect, Dr. Truty says. "We know if the tumor is dead after chemotherapy, then an operation will allow patients to live longer, compared to patients whose tumors are still alive at the time of surgery."
In their American Journal of Roentgenology study, "Borderline Resectable and Locally Advanced Pancreas Cancer: FDG PET/MRI and CT Tumor Metrics for Assessment of Neoadjuvant Therapy Pathologic Response and Prediction of Survival," Dr. Panda and the study team sought to assess how pancreatic tumors responded to therapies and predict overall survival using PET/MRI and CT data.
The study team determined that PET/MRI provides a noninvasive selection tool to decide whether a surgery will benefit the patient in the long run, and whether a timely switch to alternate treatment regimens could optimize a patient's chances for favorable long-term outcomes.
Ajit Goenka, M.D., a Mayo Clinic radiologist and senior author of the study, says the realization of PET/MRI's potential in pancreatic cancer has led to a major shift in how it is used, providing surgeons like Dr. Truty with a clearer picture of whether therapies are working in patients and guiding next steps..
With the metrics obtained through PET/MRI and CT, the researchers found that Mayo Clinic specialists could tailor care to each patient's disease profile.
"We've probably done over 1,000 PET/MRIs. In this particular study, we found that the PET/MRI was much better in predicting how cancer would respond than regular CT scans or blood tests that we normally would use. And that's how this is really changing the practice," Dr. Truty says. "The first thing I want to see after my first visit with the patient after they get their first rounds of chemotherapy is what is the PET/MRI telling me? And then we make significant treatment decisions based on that PET scan."
A version of this story was originally published on Mayo Clinic's Advancing the Science blog.
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