Advancements in Radiation Oncology Continue to Improve Lifesaving Care

Mark Bonnen, MD

At the turn of the 20th century, excitement over the emergence of radiation therapy to destroy tumors was quickly tempered by the discovery that this same radiation could also cause cancer. Pioneering radiologists testing the intensity of the radiation beam on their own arms, looking for just the right shade of pink, often developed leukemia years later from the repeated exposure. This paradox did not go unnoticed and radiologists have made huge leaps in technology in the last few decades to make sure they stay on the right side of the line between cause and cure.

Radiation is a powerful tool used as the primary treatment in more than 50 percent of cancers and involves multiple disciplines and technologies. Mark Bonnen, MD, serves as chair of the Department of Radiation Oncology at UT Health San Antonio’s Joe R. and Teresa Lozano Long School of Medicine and chief medical officer at the Mays Cancer Center.

Advancements in aiming and modulating the radiation beam, improving imaging of tumor targets, and even the atomic makeup of the beam itself have all moved the field forward.

Advancements in aiming

Intensity Modulated Radiation Therapy (IMRT): A high dose of radiation is delivered to the tumor and a very low dose in adjacent tissues within millimeters. Computer driven tungsten wafers (called a multileaf collimator) move in and out of the path of the radiation beam to shape the beam to conform to the contours of the tumor.
Stereotactic Body Radiation Therapy (SBRT): Radiation dose distribution is finely tuned to conform to the tumor. Focuses the beam from many angles to avoid critical adjacent organs.

Advancements in target imaging

Motion management: CAT scans of the tumor are taken over a period of time and integrated into a computer system to generate a “4-D scan” that maps out tumor movement over time as the patient breathes.
Gating: Treatment is delivered in shorter bursts during deep inhalation as patients hold their breath. A laser grid is projected over the patient’s body and any distortions on the grid caused by movement are measured by an optical scanner to assure the patient remains in correct position.
Image-Guided Radiotherapy (IGRT): Advanced MRI imaging is integrated into the beam guidance system.

Advancements in radiation particle therapy

Proton therapy: Advanced form of radiation therapy uses a powerful beam of proton particles which only release their full energy payload at the precise location, contour, and depth of the tumor.

IMRT has been around for about 20 years, says Dr. Bonnen. “Unfortunately, you can only get so far with that system using standard radiotherapy, which
uses photon particles, before those pesky laws of physics start to give you grief.” The Mays Cancer Center is in the final planning stages of building a proton therapy facility which will soon break ground.

“Unlike photons which come in one side of the body and go out the other, protons actually stop,” explains Dr. Bonner. “When you couple proton therapy with the precision of the IMRT technology, you can really begin to finesse some things.” Proton therapy offers a huge advantage in treating children especially, since any amount of unwanted radiation when photons exit the body can cause potential serious developmental issues.

How new technology is administered is equally important. “One of the values of receiving care at a National Cancer Institute-designated Cancer Center is that there is no single practitioner in isolation that is making a decision about your care. Everything is a collaboration,” Dr. Bonnen says. Patient cases are routinely presented before “tumor boards” – composed of medical and surgical oncologists, radiologists, pathologists, residents and even faculty from partner MD Anderson Cancer Center – who review patient history, imaging and findings. “Then, as a team, we’ll come up with the best possible plan of action for that particular patient.”

Teams use applied data analytics to keep track of complicated treatment plans and establish benchmarks. An automated dashboard provides updates on patient status showing who is on track or about to fall behind in their treatment. It takes an average of 12 days to get a new patient started in his or her treatment plan, says Dr. Bonnen, with multiple contacts with appropriate specialists. “Any delay is a problem in our field. For example, in head and neck cancer, as well as cervical cancer, once patients have started on their course of therapy, each day of delay decreases their chance of cure, and so this is an extremely important matter.”

Technical advances will merge with an increasing understanding of tumor biology, Dr. Bonnen predicts, in a final frontier of “adaptive radiation” where a patient’s daily treatment plan is adjusted as quickly as the biology of his tumor changes. “I think the Mays Cancer Center is going to play a significant role in that,” he says.

“I’m not the kind of guy who likes a status quo job. I like going places. I have found the leaders here to be very purposeful in their goals and initiatives, and skilled in their ability to voice a vision: ‘This is where we’re headed folks, and this is a tremendous place we’re going to,’ ” he said.