Staphylococcus aureus has been shown to play a role in the pathogenesis of some inflammatory skin diseases such as atopic dermatitis. Whether the bacteria can also trigger or exacerbate radiation dermatitis is still unclear. In theory, the disruption of the skin barrier by radiotherapy could contribute to the proliferation of the bacteria and set pro-inflammatory processes in motion.
The New York research team got to the bottom of this with two studies. In a first study, they wanted to clarify whether there is an association at all between colonisation with Staph. aureus and ARD. For their prospective cohort study, they recruited 76 patients with breast cancer (n=41) and head and neck cancer (n=34) who were scheduled for curative fractionated radiotherapy with a total radiation dose of 58.8 Gray (Gy).
Before the start of treatment, swabs were taken from the nose, the irradiated skin area and the opposite side. The swabs were repeated during the last week of radiotherapy. Pre-therapeutically, 16 people (21.1%) had a positive nasal swab.
During treatment, all 76 participants suffered acute radiation dermatitis, most grade 1, but about one third grade 2 or 3. In this third, the prevalence of nasal colonisation before the start of treatment was higher than in those who developed only mild ARD (34.5% versus 12.8%). At the end of therapy, the colonisation rate on the nose and skin was also significantly higher in patients with ARD grade 2 and above than in those with ARD grade 1.
For the researchers, this suggested a connection between nasal colonisation with Staph. aureus and the development of higher-grade ARD.
Kost and colleagues addressed this question in a second randomised clinical trial. This time, 77 patients with the same diagnoses were included. Of these, 39 received antimicrobial treatment with mupirocin nasal ointment 2% twice daily and chlorhexidine gluconate 4% wash lotion once daily, before treatment and every fortnight during treatment. The comparison group of 38 participants received normal basic hygiene.
The result: after bacterial decolonisation, none of the 39 patients suffered a higher degree of ARD, compared to just under a quarter in the control group. The treatment was also very efficient. Colonisation rates in the intervention group fell from 10.8% before treatment to 5.4% afterwards, while they rose from 16.2% to 24.3% in the control group.
The two studies suggest a connection between colonisation with Staph. aureus and the development of acute radiation dermatitis. According to the authors, simple, safe and cost-effective preventive measures can be derived from this. They argued that all cancer patients should be given antibacterial prophylaxis before radiotherapy, regardless of the screening results.