Researcher to Present Study on Using MRI-guided Linear Accelerator System to Track Glioblastoma Progression

Kaylie Cullison, MD/PhD student

Among the many innovative labs at Sylvester Comprehensive Cancer Center lies the one belonging to Eric A. Mellon, MD, PhD, co-leader of Sylvester’s Neurologic Cancer Site Disease Group and radiation oncologist. In his lab, novel discoveries advance therapies for glioblastoma while he invests in the next generation of researchers through mentorship.

Together with his mentees, Dr. Mellon is learning more about tumor growth in brain cancer. Using an MRI-guided linear accelerator system, known as MRI-Linac, Dr. Mellon and Kaylie Cullison, a dual-degree candidate at the University of Miami Miller School of Medicine’s Medical Scientist Training Program, have found pattern and volume changes that may help physicians understand if patients are responding to treatment.

Cullison will be presenting their findings at this year’s American Society for Radiation Oncology (ASTRO) conference, Oct. 1-4 in San Diego, Calif.

“Knowing if it’s true progression, indicative of a poor response to treatment, or pseudoprogression, a favorable response that may look worse due to swelling or tumor necrosis, is essential for clinicians,” said Dr. Mellon.

Glioblastoma is the most common brain cancer and, with only a 10% chance of patient survival, one of the deadliest. Current treatment involves surgery to remove the tumor, followed by standard chemotherapy and radiation with an MRI follow-up. Issues arise when tumor growth occurs during treatment, making it difficult to determine the effectiveness of the therapy and whether the change is due to cancer progression.

“Chemotherapy and radiation delay the amount of time it takes for this cancer to come back, but it almost always makes a return,” Dr. Mellon said. “My lab is strategically combining novel imaging techniques to deliver effective and targeted radiation therapies.”

Effective Collaboration in Glioblastoma Therapy

Standard radiation therapies for glioblastoma use a CT-guided linear accelerator to target cancer cells. This treatment has its shortcomings since it can only provide images of the skull and not the brain tumors inside the skull.

The merger of MRI and linear accelerators allowed Dr. Mellon to apply the same technology to brain tumors, a first in the field.

“Despite the scientific community telling me this idea was pointless, I had a feeling there was use in this technology for brain tumors,” Dr. Mellon said. “We were the first in the world to start looking at glioblastoma changes daily during radiation therapy, and now we are seeing its effectiveness in more accurate treatment.”

The Impact of a Physician-Mentor

Cullison is leading some of this strategic research in Dr. Mellon’s lab. She has been Dr. Mellon’s mentee since 2018 and previously spent two years as a fellow with the National Institutes of Health working with MRI imaging data. She’s been passionate about medicine since childhood, and her time as a fellow solidified her desire to pursue a career as a physician-scientist.

“I first did a research rotation with Dr. Mellon when I began my program at the Miller School in 2018, as both of our interests aligned in MRI, imaging data and the brain,” Cullison said. “Even before he had funding, I knew he would be my mentor, as I believed in his ideas and enjoyed the work at his lab.”

“It’s been an enormous pleasure having Kaylie in my lab,” Dr. Mellon added. “It is through Sylvester’s support that I have transitioned into a clinician-scientist and can mentor Kaylie and everyone else in my laboratory. Supporting junior faculty pays forward to advance the future of medicine.”

With Dr. Mellon’s guidance, Cullison is currently working on determining if daily monitoring of tumor changes during a course of MRI-guided linear accelerator therapy could result in early prediction of treatment response.

“This project will provide clinically useful tools for physicians treating glioblastoma, fulfilling an unmet need in glioblastoma management by allowing adaptation during treatment for growing tumors,” Cullison said. “If successful, we will be able to predict patient outcome during treatment much earlier than current methods, which could allow for intensification of therapy in poorly responding patients.”

Growth Environment

Cullison’s presentation at ASTRO is a full-circle moment for Dr. Mellon. As an M.D. and Ph.D. who trained in a similar program, he takes great pleasure in fostering the next generation of physician-scientists in his lab.

Mentorship, to Dr. Mellon, involves having a solid sense of one’s shortcomings and areas of excellence to be effective. He designed his lab as a place filled with different personalities, strengths and career goals, so members can build and complement one another.

“I have made it a priority to provide various avenues of sponsorship for my mentees by promoting their careers and creating opportunities for them,” Dr. Mellon said. “In return, a good mentee will under promise and over deliver. Kaylie has been an ideal mentee in more ways than one. I have even learned more about myself and my approach to mentorship, and even bettered my interpersonal dynamics through her.”

“I lucked out and found a lab in Dr. Mellon’s where I felt supported by an adaptable and open-minded mentor,” Cullison added. “Not only have I been able to learn a great deal about radiation oncology, but I have been given the opportunity and support to lead my research projects, advance my professional development, and witness firsthand the grit and determination that it takes to become a successful physician-scientist in the process.”