UW Veterinary Care Cancer Patients To Benefit From New, More Precise Radiation Therapy Delivery System

Certified veterinary technician Abigail Jones holds Davis, a 14-year-old domestic short-haired cat who received radiation therapy treatment for nasal carcinoma with the new Radixact machine
Certified veterinary technician Abigail Jones holds Davis, a 14-year-old domestic short-haired cat who received radiation therapy treatment for nasal carcinoma with the new Radixact machine.

Written by Meghan Lepisto

Oncology patients undergoing radiation therapy at UW Veterinary Care will now receive treatments with an adaptive, motion-tracking radiotherapy system. The cutting-edge machine, installed in fall 2020, provides several advantages for companion animals and their care providers, from precision to speed to new treatment possibilities.

“With this technology, we can now treat tumors and spare healthy tissue with more confidence and more accuracy, in addition to targeting tumors in areas of the body that we couldn’t previously,” says Professor Lisa Forrest, head of UW Veterinary Care’s Radiation Oncology Service.

Most significantly, the new Radixact system provides real-time motion tracking of tumors and synchronizes treatment delivery. As a tumor moves, treatment moves with it — the radiotherapy delivery beam is continuously synchronized to the tumor position.

Radixact radiation therapy treatment delivery system
The Radixact radiation therapy treatment delivery system. Photo: Ron Collins/Accuray

For example, during treatment of a lung tumor, as a patient’s lungs expand and contract with each breath, the machine tracks the moving tumor and adapts the beam’s location. This ensures accurate delivery of the treatment dose and better sparing of the surrounding normal tissue.

“In real time the machine will track the tumor’s location, meaning we can now reduce the tumor target size — allowing accurate dose delivery to the tumor and reduced dose to normal tissues,” Forrest explains.

The real-time tracking and adaptation opens up new treatment opportunities for cancers in the abdomen and thorax — such as lung, heart, liver, and kidney tumors — where the close proximity of vital organs and other sensitive tissues made radiation therapy previously difficult or impossible.

In addition, the technology provides quicker, more detailed computed tomography (CT) imaging during pre-treatment positioning to help align patients for treatment with more precision. It also offers refined tumor dose accuracy, delivery, monitoring, and adaptation.

“Treatments are, on average, shorter than before, and the quality of each radiation plan has increased,” says Nate Van Asselt, a clinical assistant professor of radiation oncology. “We can ensure that the tumor gets all the radiation it needs while the sensitive organs close to the tumor get as little radiation as possible.”

The machine automatically monitors how tumors change in size during treatment and any time the radiation beam reaches surrounding normal tissue. Then it immediately alerts the clinical team that changes to the treatment plan may be necessary. It also calculates any difference between each planned treatment dose and the amount delivered.

The Radixact software allows clinicians to evaluate how tumors have changed during treatment and review the dose they received
The Radixact software allows clinicians to evaluate how tumors have changed during treatment and review the dose they received. This oral melanoma tumor (outlined in red) grew slightly between the treatment planning period and the start of treatment, so there is a difference (displayed in the top row) between the planned dose calculated for treatment (middle row) and the delivered dose (bottom row). With awareness of this discrepancy, clinicians can then correct the dosage.

“Changes in the size of the tumor affect the treatment dose that is actually received, compared to what we planned for it to receive,” notes Michelle Turek, a clinical associate professor with the Radiation Oncology team. “This software allows us to evaluate how tumors have changed during treatment and to review the dose they received. If there is a discrepancy between the planned dose and the delivered dose, then we have an opportunity to correct it.”

UW Veterinary Care is currently the only veterinary medical hospital globally to offer this treatment. Gifts to the UW School of Veterinary Medicine’s Pets Make a Difference Fund — inspired by the late golden retriever Scout, whose cancer journey and care provided at the UW School of Veterinary Medicine were spotlighted in WeatherTech’s 2020 Super Bowl commercial — helped make possible this significant equipment upgrade.

Funds raised by the Super Bowl commercial and from other generous donors are being used to support research at the school to better diagnose, treat, and prevent cancer, and to purchase specialized equipment that will help clinicians and researchers identify new cancer-fighting drugs and treatments — discoveries that are shared with the world.

“This generous support will continue to benefit not only patients of our hospital but pets and people battling cancer all across the world as our clinical findings translate to innovations in treatments and technology,” says UW Veterinary Care Director Ruthanne Chun DVM’91. “We are so thankful.”

Successful clinical trials in dogs with nasal tumors at UW Veterinary Care, shepherded by Professor Lisa Forrest, led to widespread use of TomoTherapy in human medicine
Successful clinical trials at UW Veterinary Care, shepherded by Professor Lisa Forrest, pictured, led to widespread use of TomoTherapy in human medicine.

The Radixact machine builds on the TomoTherapy radiotherapy delivery system that UW Veterinary Care previously utilized. This radiation machine built into a CT scanner was developed at UW–Madison. Successful clinical trials in pet dogs with nasal tumors at UW Veterinary Care in the early 2000s, shepherded by Professor Forrest, led to TomoTherapy’s widespread use in human medicine worldwide.

Oncologists at the UW School of Veterinary Medicine are world-renowned for advancing clinical treatments and technologies for dogs and cats with cancer. The school is also a leader in comparative oncology research, where companion dogs and cats (with owner consent) are included in clinical trials to investigate new cancer therapies with the goal of informing clinical treatments with better effectiveness and less toxicity in both animal and human patients.

This article appeared in the Spring 2021 issue of On Call magazine.


« Back to News