Michigan Medicine, in a recent collaboration with other medical centers, conducted a study to test whether computer-enhanced radiotherapy reduces skin irritation and pain in breast cancer patients and improves treatment efficacy.
The treatment is called planned inverse, intensity-modulated radiotherapy. It was found to reduce these side effects more effectively 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 while attacking tumors, or aligning with a tumor, according to the University of Alabama School of Medicine. The Michigan Consortium for Quality Radiation Oncology, the organization that initiated the study, reports that the use of reverse-planned IMRT instead of 3D CRT significantly reduces the acute toxicity of breast radiotherapy.
Reshma Jagsi is vice chair of radiation oncology and director of the Center for Bioethics and Social Sciences in Medicine at Michigan Medicine. Jagsi was also lead author on the study and explained that planned IMRT is beneficial because instead of treating tissue through a single beam of uniform intensity, this treatment makes it possible to alter the regularity of the radiation beam.
“If you treat that half for a certain amount of time, then block it, and keep processing that (other) half for more then one half of the field gets denser than the other,” Jagsi said. “You can do it brazenly and break (the ray) in half. You can break it down into shapes, clips, and you can even change the density pixel by pixel. This requires computerized treatment planning and optimization.”
Inverse mapping IMRT works by using specialized computers to calculate the dose of radiation needed for specific parts of a tumor. According to the National Library of Medicine, the computer calculates a “merit figure” or “the ratio between the tumor dose delivered and the normal tissue dose” to ensure the maximum efficacy of radiotherapy.
Radiation oncologist Frank Vecini assisted with the data analysis and was a co-author of the study manuscript. He said the study was significant because it showed, for the first time, the effect of IMRT compared to 3D patients.
“I think what sets this apart is that it’s one of the largest, if not the largest, database now that the docs that patients treated with planned IMRT weren’t significantly better, but were better than 3D patients,” said Vicchini. . “Patients treated with the 3D technology performed very well, but this shows that IMRT, a more complex technique, resulted in a 5% to 10% reduction in acute toxicity experienced by patients.”
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 remain questions to consider with the development of reverse-planned IMRT, such as whether the additional economic cost of using reverse-planned IMRT is possible for patients and whether patients can still use 3D CRT in more effective ways.
“There is no doubt that patients (using reverse scheme IMRT) did better, but is this something that can only be achieved with IMRT?” Vicini said. “Or when we find out what really happened… can we do the same with 3D (treatment)?”
Many researchers continue to study the reverse-scheme IMRT. When asked about her motivations for participating in the study, Gagsi said it was important to consider the side effects of the treatment on patients.
“One of the great things about breast cancer treatment these days is that we are often able to cure the disease and have long-term survivors,” Gagsi said. “This makes us particularly aware of the side effects of the treatments we offer and how we can ensure that the treatments we offer are acceptable to our patients so that they can receive full treatment and not suffer, and continue to live long, healthy and productive lives with the great quality of life we want them to.”
Daily staff correspondent Rachel Mintz can be reached at email@example.com.