Michigan Medicine, in a recent collaboration with other medical centers, conducted a study to test if computer-optimized radiation therapy lessened skin irritation and pain for breast cancer patients and improved treatment effectiveness.
The treatment is named inverse-planned, intensity-modulated radiotherapy. It was found to more effectively reduce these side effects than three-dimensional conformal radiotherapy (3D CRT), which is commonly used to treat many types of cancer, including breast cancer.
3D CRT treats cancer by sending radiation from multiple angles with the intent of protecting healthy tissue but attacking tumors, or conforming to the tumor, according to the University of Alabama’s School of Medicine. The Michigan Radiation Oncology Quality Consortium, the organization that initiated the study, reported that using inverse-planned IMRT rather than 3D CRT significantly decreases acute toxicity of breast radiotherapy.
Reshma Jagsi is the deputy chair of Radiation Oncology and the director of the Center for Bioethics and Social Sciences in Medicine at Michigan Medicine. Jagsi was also a lead author on the study and explained that inverse-planned IMRT is beneficial because instead of treating tissue through a single beam of uniform intensity, this treatment makes it possible to change the uniformity of a beam of radiation.
“If I treat this half for a certain amount of time, and then I block it, and I keep treating this (other) half for more, half of the field has gotten more intensity than the other,” Jagsi said. “You can do that crudely and just break (the beam) in half. You can break it into shapes, segments, and you can even vary the intensity pixel by pixel. And that requires computerized treatment planning and optimization.”
Inverse-planned IMRT works by using specialized computers to calculate the dose of radiation necessary for specific parts of a tumor. According to the National Library of Medicine, the computer calculates a “figure of merit,” or “the ratio between the delivered tumour dose and normal tissue dose,” to ensure maximum effectiveness of the radiation therapy.
Radiation Oncologist Frank Vicini helped analyze the data and was a co-author of the study’s manuscript. He said the study was important because it showed, for one of the first times, the effect of IMRT compared to 3D patients.
“I think the uniqueness of this is that it’s one of the largest, if not the largest, database now that documents that the patients treated with the inverse-planned IMRT did, not dramatically better, but did better than 3D patients,” Vicini said. “The patients treated with even the 3D did very well, but this is showing that the inverse-planned IMRT, the more sophisticated technique, did result in a 5% to 10% reduction in acute toxicity that the patients experience.”
As Vicini said, this study was one of the largest of its kind, comparing data from 23 institutions from 2011 to 2018.
Vicini noted that there are still questions to consider as inverse-planned IMRT develops, such as whether the additional economic cost of using inverse-planned IMRT is feasible for patients and if patients can still use 3D CRT treatment in more effective methods.
“There’s no question that the patients (using inverse-planned IMRT) did better, but is it something that can only be achieved with IMRT?” Vicini said. “Or, in learning what actually happened … can we actually do the same thing with the 3D (treatment)?”
Many researchers are continuing to study inverse-planned IMRT. When asked about her motivation for participating in the study, Jagsi said it is important to consider the side effects treatment has on patients.
“One of the neat things about treating breast cancer these days is that we often are able to cure the disease and have long term survivors,” Jagsi said. “And so that makes us particularly mindful of the side effects of our treatments and how we can make sure that the treatments we’re administering are tolerable for our patients so that they can receive the full treatment and not suffer, and go on to live the long, healthy, productive lives with great quality of life that we want for them.”
Daily Staff Reporter Rachel Mintz can be reached at mintzrac@umich.edu.