Association of Staphylococcus aureus Colonization With Severity of Acute Radiation Dermatitis in Patients With Breast or Head and Neck Cancer.

Importance:Pathogenesis of acute radiation dermatitis (ARD) is not completely understood. Pro-inflammatory cutaneous bacteria may contribute to cutaneous inflammation after radiation therapy. Objective:To evaluate whether nasal colonization with Staphylococcus aureus (SA) before radiation therapy is associated with ARD severity in patients with breast or head and neck cancer. Design, Setting, and Participants:This prospective cohort study with observers blinded to colonization status was conducted from July 2017 to May 2018 at an urban academic cancer center. Patients aged 18 years or older with breast or head and neck cancer and plans for fractionated radiation therapy (≥15 fractions) with curative intent were enrolled via convenience sampling. Data were analyzed from September to October 2018. Exposures:Staphylococcus aureus colonization status before radiation therapy (baseline). Main Outcomes and Measures:The primary outcome was ARD grade using the Common Terminology Criteria for Adverse Event Reporting, version 4.03. Results:Among 76 patients analyzed, mean (SD) age was 58.5 (12.6) years and 56 (73.7%) were female. All 76 patients developed ARD: 47 (61.8%) with grade 1, 22 (28.9%) with grade 2, and 7 (9.2%) with grade 3. The prevalence of baseline nasal SA colonization was higher among patients who developed grade 2 or higher ARD compared with those who developed grade 1 ARD (10 of 29 [34.5%] vs 6 of 47 [12.8%]; P = .02, by χ2 test). Conclusions and Relevance:In this cohort study, baseline nasal SA colonization was associated with development of grade 2 or higher ARD in patients with breast or head and neck cancer. The findings suggest that SA colonization may play a role in the pathogenesis of ARD.