SPOTLIGHT EDUCATION
BEAMING WITH INSIGHT Dr. Everett ' s Elective Rotation Investigating Proton Dosimetry and Physics
By: Ashlyn Everett, M. D. | UAB Radiation Oncology Resident
ABOVE: The University of Florida proton gantry where Dr. Everett completed her elective rotation.
Along the sunny coast of Florida, there is another form of energy beaming down on the residents of Jacksonville. In 2006, the University of Florida opened a proton facility with three proton gantries, one proton beam line room, and two LINAC gantries. Their facility treats between 100-120 proton patients daily, operating from 6:00 am until well after midnight most nights to accommodate their patient volume.
During the month of December, I had the opportunity to visit their bustling facility to learn about the clinical and dosimetric advantages or disadvantages with proton therapy. I spent a majority of my time working under physicians treating prostate, lymphoma, lung, or head and neck cancers.
In the clinical realm, proton therapy is similar to conventional photon therapy, with the theoretical benefit of less toxicity due to less normal tissue exposure to ionizing radiation. However, I also observed some patients with brisk skin reaction after head and neck proton radiation due to the high surface dose. My primary goal while at the UF Proton Institute was to learn the unique features of proton dosimetry and physics, from a physicians’ perspective.
First, I learned that treatment response during radiation greatly affects proton therapy as compared to conventional photons. Tumor shrinkage can lead to changes in dose distribution, both to tumor and normal structures, further complicating proton therapy. In some situations, patients required multiple imaging scans and updated plans to account for the change in tissue density, most notably in the treatment of lung tumors.
This required coordinating a large team of nurses, dosimetrists, therapists, and physicians to provide the best care for patients. Fortunately, there was a solid infrastructure supporting these unique issues relating to proton therapy.
Second, I learned that proton treatment can offer dosimetric advantage compared to photon therapy in appropriately selected patients. While on my elective rotation, I participated in a retrospective dosimetry study investigating the role of proton therapy for patients with mediastinal lymphoma. For a series of 22 patients, we compared IMRT photon to proton therapy, and looked at the doses to organs at risk including the heart, lungs, esophagus, thyroid, and nontarget body tissues. Protons therapy significantly reduced dose to these normal tissues; however, the clinical benefit of these findings remains unknown. Our results were submitted to ASTRO for presentation at the 60th annual meeting this fall, and we are excited to share these results with the radiation oncology community.
Proton therapy is an exciting treatment option for many patients, and I am looking forward to having it at UAB for our patients. While similarities with photon treatment exist, there are specific issues relating to proton therapy that require an astute team of physicians, dosimetrists, and physicists. Delivering appropriate care requires seamless team coordination and attention to detail to ensure that our proton therapy is accurate and precise. I am confident that UAB will continue to provide excellent care as we have the exciting opportunity to provide proton treatment to patients in Alabama and across the Southeast.
17 | RAYS OF HOPE