During radiotherapy, some cancer patients develop radiodermatitis, a severe inflammation of the skin. A recent study suggests that skin bacteria play an essential role in this: Breast cancer patients whose skin microbiome was disturbed prior to treatment also developed radiodermatitis.
Until now, it was largely unclear why radiodermatitis only affects some of those treated. The new study by the Technical University of Munich (TUM) and its Klinikum rechts der Isar in cooperation with the University of Augsburg and Helmholtz Munich has investigated the role of microbes on the skin in this regard. "The skin microbiome consists of hundreds of different kinds of microorganisms," explains Claudia Hülpüsch, head of functional microbiomics at the Chair for Environmental Medicine at the University of Augsburg. "Some of them, the so-called commensal bacteria, are present in healthy people in a relative higher number and are part of the skin barrier. They act as natural protection, preventing the proliferation of harmful bacteria or fungi, for example."
20 patients examined
The researchers examined 20 women with breast cancer for their pilot study. All participants received radiation therapy for a period of seven weeks. Before the first session and thereafter weekly, the researchers took two skin swabs from each patient - one from the irradiated breast and one from the non-irradiated breast. In these swabs, they determined the number and composition of microorganisms. "Through the analysis we determined that before beginning the radiotherapy four women had unusual skin microbiome," explains 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."
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. 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.
Disinfection reduces likelihood of dermatitis
"The composition of skin bacteria before radiotherapy appears to indicate which women have a particularly high risk of developing radiodermatitis," says Dr. Kai Borm, a researcher at TUM's Clinic of Radiation Oncology and Radiation Therapy. "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 patients with other cancer types, such as those in the throat, nose, and ear, or with sarcomas, as these patients have a particularly high risk of severe radiodermatitis."
The researchers see significant potential in these results and are already thinking about the next steps, planning larger studies with more patients and different types of tumors to validate the results. The goal is both the prediction and targeted prevention of radiodermatitis.
C. Hülpüsch, A. U. Neumann, M. Reiger, J. C. Fischer, A. de Tomassi, G. Hammel, C. Gülzow, M. Fleming, H. Dapper, M. Mayinger, C. Ertl, S. E. Combs, C. Traidl-Hoffmann, K. J. Borm. "Association of Skin Microbiome Dynamics With Radi-odermatitis in Patients With Breast Cancer". JAMA Oncology (2024) ; DOI:10.1001/jamaoncol.2023.6533.
