Revolutionary Research at Mayo Clinic

Dr Brittany Siontis

Dr. Brittany Siontis, Mayo Clinic Physician and Researcher

by Miranda Mead

Brittany Siontis spent her first six months as a first-year fellow at the Mayo Clinic working closely with sarcoma cancer patients. Siontis was fascinated with the variety of sarcomas and loved treating patients of all ages. But her continued frustration of, “not knowing,” drove her into sarcoma oncology research to devise solutions to better treat sarcoma.

In the beginning of her research, Siontis asked, “Is there something that we can test in the blood to figure out what a patient’s cancer is doing?” Siontis chose to focus on circulating tumor DNA, because these markers circulate in the blood and are specific to each patient’s cancer. Developing new technology around these blood markers would allow doctors to determine what the cancer looks like without doing a biopsy. Biopsies are invasive, can be painful, and pose a high risk for infection and bleeding.

As an example, there is a specific type of lung cancer that has a mutation called EGFR. Scientists can look in a patient’s cells to see if the EGFR mutation is circulating in the blood, which would indicate how much cancer is present. Similarly, in Ewing Sarcoma – an aggressive bone/soft tissue cancer – there is a marker present in the blood called pathognomonic translocation. Scientists can pick out this biomarker to know how to better treat each patient.

Scientists know there are specific DNA markers associated with specific cancers, such as Ewing Sarcoma. The hope is to take that knowledge and apply it more broadly to other sarcoma cancers. Siontis started asking, “is there enough circulating tumor DNA that we can even detect it in the blood?”

To start the process, if a patient had a biopsy or surgery done on his or her tumor, Siontis’ team conducts comprehensive genomic sequencing on a piece of the tumor. This process includes looking at the tumor’s DNA and RNA to see if there are any genetic changes. Since each tumor is going to have its own mutations, doctors can give the patient individualized care based on the tumor’s present biomarkers.

In addition to genomic sequencing, Siontis’ team is working to determine the amount of circulated tumor DNA needed to accurately monitor a patient’s tumor. Prior to treatment, blood is taken to measure circulating tumor DNA. While the patient goes through treatment, doctors can see how much circulating tumor DNA there is with each blood draw. In conjunction with imaging, the circulating tumor DNA can help determine how the cancer is responding to the treatment. This combination of images and blood work also helps with early detection of cancer recurrence, significantly improving survival rates.

Siontis and team are doing exciting research that has the capability to positively impact how sarcoma cancers are detected, monitored and treated.