Bacterial Decolonization Reduces Severity of Acute Radiation Dermatitis

While staphylococcus aureus may play a role in the development of acute radiation dermatitis (ARD) in patients undergoing radiation therapy, bacterial decolonization (BD) can decrease the severity of the condition, particularly among those with breast cancer, according to two studies published in JAMA Oncology.

In a phase II/III randomized trial of 75 patients with breast cancer and two with head and neck cancer, no patients treated with BD developed grade ≥2 ARD with moist desquamation compared with 23.7% of patients treated with standard of care (P=0.001), reported Beth McLellan, MD, of Montefiore Medical Center and Albert Einstein College of Medicine in the Bronx, New York, and colleagues.

Similar results were noted among just the 75 patients with breast cancer (0% vs 21.6%, respectively, P=0.002).

When the primary analysis was repeated using the originally prespecified primary endpoint of grade 2 including patients with or without moist desquamation, rather than grade 2 ARD with moist desquamation, "the results trended in the same direction," the team reported (35.9% treated with BD vs 52.6% treated with standard of care, P=0.14).

In addition, the mean ARD grade was significantly lower for patients treated with BD compared with those treated with standard of care (1.21 vs 1.62, P=0.02).

"The results of this randomized clinical trial suggest that BD is effective for ARD prophylaxis, specifically for patients with breast cancer, and support the further investigation of BD for ARD prophylaxis, which is a safe and widely available regimen, for patients with cancer," McLellan and team wrote.

In the other study that included a prospective cohort of 76 patients with breast or head and neck cancers, also conducted by McLellan and colleagues, the prevalence of baseline S. aureus nasal colonization was 34.5% in patients who developed grade 2 or 3 ARD compared with just 12.8% of patients who developed grade 1 ARD (P=0.02).

Regression modeling showed an association between baseline S. aureus nasal colonization and development of grade ≥2 ARD (OR 4.24, 95% CI 1.24-14.51, P=0.02).

"This finding suggests that in patients who are colonized in the nares at baseline, radiation-induced disruption of the skin barrier may allow [S. aureus] to proliferate on the skin, amplifying the inflammatory process," McLellan and team noted.

ARD affects up to 95% of patients with cancer treated with radiation therapy. It presents within 90 days of radiation initiation as skin erythema and may turn into dry or moist desquamation, full-thickness ulceration, or necrosis. ARD may have negative effects on patients' quality of life and can change treatment plans. However, treatment options are limited.

The randomized trial, conducted from June 2019 to August 2021, included 80 patients, 77 of whom completed radiation therapy; 39 of the 77 were treated with BD, a multi-day regimen of intranasal mupirocin ointment application and chlorhexidine body cleanser, which "has been shown to be safe and cost-effective in several clinical settings," according to McLellan and colleagues.

The other 38 patients who completed RT were treated with standard of care -- normal hygiene and emollients.

Mean age was 59.9 years. All of the breast cancer patients were women, and the two head and neck cancer patients were men. Most patients were Black (33.7%) or Hispanic (32.5%).

The median total radiation dose was 52.4 Gy delivered at a median of 20 fractions. Five patients received chemotherapy concurrently with radiation, and 41 patients received chemotherapy prior to radiation.

Baseline nasal colonization with S. aureus was seen in 13% of patients.

Of the patients who received BD, 69.2% reported adherence to the regimen, and one withdrew from the trial due to itch.

McLellan and colleagues noted that BD was associated with lower ARD grade even when adjusting for known ARD risk factors, such as higher body mass index and radiation dose.

"Interestingly, our BD regimen was successful despite an unexpectedly low baseline incidence of S. aureus colonization," they wrote, noting that patients may also become colonized during the course of radiation therapy, given the frequency of visits to healthcare facilities.

"For these reasons, we recommend universal BD regardless of baseline S. aureus colonization status," they added.

The prospective cohort study, conducted from July 2017 to May 2018, included 76 patients -- 59.9% with breast cancer and 46.1% with head and neck cancer. Mean age was 58.5 years, and 73.7% were women. There were no differences in clinical or demographic characteristics between the two groups.

Patients received a mean total radiation dose of 58.5 Gy delivered in a mean number of 28.0 fractions. At the completion of radiation therapy, the S. aureus colonization rate at every tested site, including nares, radiated skin, and contralateral skin, was significantly greater among patients who developed grade ≥2 ARD compared with patients who developed grade 1 ARD.

"A better understanding of the association between bacterial colonization and ARD pathogenesis is crucial as it can inform how to treat patients who develop ARD," McLellan and team noted.

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