Markerless Radiation Erases a Reminder and Improves Breast Cancer Therapy

By Asal Rahimi, M.D., M.S. and David Parsons, Ph.D.

Breast cancer almost always leaves its mark on patients. Along with surgical scars and changes in breast size and shape, medical tattoos or semi-permanent marker dots and lines were drawn on the patient’s chest to align radiotherapy beams, like checkpoints on a map.

Seeing those marks was a constant reminder for patients of the journey they never asked to take. Many reported feeling self-conscious wearing dresses or blouses that might reveal the dots or lines, adding further discomfort after enduring treatment.

We knew there had to be a better way. So in 2013, we embarked on a 10-year initiative to deliver markerless radiation therapy to our breast cancer patients, and today it has become the standard of care at the Department of Radiation Oncology at UT Southwestern’s Harold C. Simmons Comprehensive Cancer Center.

Thanks to the determination and innovation of our medical physicists and radiation oncologists, every one of our patients gets access to markerless, surface-guided imaging, along with other internal imaging, that precisely zeroes in on their treatment site. Additionally, some patients qualify for adaptive radiation therapy, which allows us to make real-time adjustments to their radiation plan for changes such as tumor size and position, maximizing precision.

UT Southwestern is the only center in Texas and one of few in the world to use this innovative dual approach, inconspicuously and privately treating our patients’ breast cancer without marking them as under therapy.

How surface-guided radiotherapy works

For each radiation therapy session, we index the patient’s body shape to the treatment couch, using their most recent CT scan as a guide. We do this so all the radiation therapy beams follow the geometry of their personal map, treating the cancer precisely and avoiding healthy tissue.

The map is generated by our motion-tracking video system, AlignRT developed by VisionRT, which uses three ceiling-mounted 3D cameras to beam a patterned light grid onto the patient’s chest. The system tracks thousands of points on a patient’s skin and matches them to the patient’s initial CT scan with submillimeter accuracy.

Radiation therapists monitor the system in real time and are alerted immediately if a patient moves as even slight movements such as breathing can move them 1-2 millimeters outside the radiation field. When this happens, the radiation therapist can turn off the machine and instruct the patient how to adjust to realign with their personal map.

We’ve been using surface-guided technology for 10 years with deep inspiration breath hold in left-sided breast cancer, in which patients fill the lungs with air and hold it for a few seconds to remain still and to buffer the heart from incidental radiation beam exposure. Our research, published in the Journal of Applied Clinical Medical Physics, showed that using surface-guided breath-hold in left-breast treatment was at least as precise and, in some cases, more precise compared with standard breath-hold radiation therapy.

Now, we’re using the technology to its full capacity by eliminating the use of physical markings for patients with left- and right-sided breast cancer.

The radiation oncologist and medical physicist work closely together to plan each patient’s care. Medical physicists have a critical role – they work behind the scenes, calibrating the machines for each patient’s treatment plan and making sure every patient gets exactly the right dose in the planned treatment field. They manage the technology and delivery, while the radiation oncologist develops the treatment plan and works face-to-face with the patients.