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Disturbed microbiome a risk factor for severe radiodermatitis

Findings from a pilot study suggest the skin microbiome plays an important role in the risk of radiodermatitis associated with cancer therapy.

In a paper published in JAMA Oncology, the investigators say their discovery may lead to a test to identify at-risk groups.

According to a press release from the University of Augsburg in Germany, one of three institutions that participated in the research, while radiotherapy is a valuable treatment for cancers, some patients tolerate worse than others, with some patients developing severe skin inflammation at the irradiated site. They note that it has been largely unclear why this only affected some of those treated.

The Technical University of Munich (TUM), and Helmholtz Munich collaborated with the University of Augsburg for this research.

In the release, investigators explain they observed breast cancer patients who had disturbed skin flora all developed severe dermatitis after radiation treatment.

“Skin flora consists of hundreds of different kinds of microorganisms,” said the study’s lead author Claudia Hülpüsch, PhD, in the release. “Some of them, the so-called commensal bacteria, are present in healthy people in a relatively higher number and are part of the skin barrier. They act as natural protection, preventing the proliferation of harmful bacteria or fungi, for example.”

Dr. Hülpüsch is head of functional microbiomics at the Chair for Environmental Medicine at the University of Augsburg.

Together with her project partner Dr. Kai J. Borm from the University Hospital Rechts der Isar at TUM, Hülpüsch examined 20 women with breast cancer. All patients received radiotherapy for seven weeks. Before the first appointment and then each week thereafter the researchers took a skin swab from each patient—one from the breast treated with radiotherapy and one from the untreated breast. From the swabs, they were able to determine the number and composition of microorganisms.

“Through the analysis, we determined that before beginning the radiotherapy four women had an unusual skin microbiome,” said Prof. Dr. Avidan Neumann from the Chair for Environmental Medicine at the University of Augsburg and researcher at Helmholtz Munich, who also participated in the study. “With these women, commensal bacteria were underrepresented. This was the case for the healthy as well as for the diseased breast. Interestingly, each of these four patients developed severe radiodermatitis during the course of radiotherapy.”

By contrast, the other 16 patients only developed mild or moderate skin damage during radiotherapy.

In the first few weeks of therapy in the four patients with underrepresented commensal bacteria, the number of bacteria developed significantly before the development of visibly severe symptoms and then decreased again near the end of therapy. With the other patients, the bacteria remained largely unchanged. This leads to the suggestion that the bacteria play a causal role in the development of radiodermatitis, the researchers say.

“The composition of skin bacteria before radiotherapy appears to indicate which women have a particularly high risk of developing radiodermatitis,” said Dr. Borm. “This helps in understanding this side-effect, enabling us to take targeted preventative measures to make radiotherapy more tolerable for patients in future.”

Initial studies show that a thorough disinfection of the skin surface reduces the likelihood of subsequent inflammation. “We are also curious to find out if our results can be transferred to other patients with tumour diseases, such as those in the throat, nose, and ear, or with sarcomas, as these patients have a particularly high risk of severe radiodermatitis.”

Prof. Dr Claudia Traidl-Hoffmann, a dermatologist and director of the Chair for Environmental Medicine, said she sees great potential in the results and is already thinking about the next steps. “We will now carry out larger studies with more patients with other tumours in order to verify the results. The goal is to be able to predict and prevent dermatitis, and this study has paved the way for this.”


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