Mupirocin-based bacterial decolonization therapy takes on radiation-induced mouth sores

Bacterial decolonization with mupirocin nasal ointment benefits nasopharyngeal carcinoma patients undergoing radiotherapy, reducing the incidence of acute radiation-induced oral mucositis (AROM) and improving quality of life by relieving pain and swallowing difficulties, according to an open-label phase III study.

In the intention-to-treat analysis, the primary outcome of severe (grade ≥3) AROM occurred in 47.7 percent of those who received routine nasal and oral care only (control group) vs 22.7 percent of those who received additional mupirocin-based bacterial decolonization therapy (relative risk, 0.48, 95 percent confidence interval [CI], 0.31–0.74; p<0.001). [JAMA Oncol 2025;11:1141-1149]

Mupirocin-based bacterial decolonization therapy was associated with 73-percent lower odds of severe AROM (OR, 0.27, 95 percent CI, 0.13–0.54; p<0.001), whereas a higher mean dose of oral radiation was associated with a nearly fourfold increase in the odds of severe AROM (OR, 3.93, 95 percent CI, 1.69–9.16; p=0.002).

The reductions in severe AROM occurred with improvements in quality of life during radiotherapy, assessed using the Quality-of-Life Questionnaire−Head and Neck 43 (QLQ-H&N43). Compared with the control group, the mupirocin group had markedly lower scores on the pain in the mouth scale (25.0 vs 50.0) and the swallowing  scale (8.3 vs 33.3).

Colonization levels of Staphylococcus aureus at the end of radiotherapy were decreased in the mupirocin group compared with the control group in both the nasal (9.4 percent vs 22.9 percent) and oral (5.9 percent vs 20.5 percent) mucosa.

S aureus is a potential pathogen in severe radiation-induced dermatitis, and mupirocin—an antibiotic that works against gram-positive organisms such as Staphylococci and Streptococci—has already been shown to reduce S aureus colonization. [JAMA 2023;330:1742-1744; JAMA Oncol 2023;9:940-945; JAMA Oncol 2023;9:962-965; JAMA Oncol 2024;10:142]

“Our findings and those of other studies highlight the strong association between S aureus and radiation damage to normal tissues in the head and neck region, confirming the effectiveness of the mupirocin-based bacterial decolonization regimen in inhibiting S aureus colonization in nasal and oral during radiotherapy,” the investigators said.

A key concern about the bacterial decolonization strategy using mupirocin is its potential impact on nasal and oral microecology. In the current study, the 16S rDNA sequencing showed no significant differences in alpha or beta diversity between the mupirocin and control groups, suggesting that bacterial decolonization therapy does not substantially alter the nasal and oral microbiomes, as the investigators noted.

Overall, “our trial’s findings propose a safe, simple, and cost-effective strategy to reduce AROM severity and provide valuable insights into its management during radiotherapy,” they said. “Nonetheless, the relationship between S aureus and AROM warrants further investigation, particularly prospective clinical studies, to clarify its underlying mechanisms.”

For the trial, a total of 176 patients (median age 52 years, 76.1 percent male) with nasopharyngeal carcinoma were randomly allocated to the mupirocin group (n=88) or the control group (n=88). Patients in both groups received standard oral and nasal care, which included a 3-min oral rinse with an ethanol extract four times daily and nasal irrigation with normal saline twice daily. Those in the mupirocin group also applied the ointment to the anterior nasal cavity twice daily for 5 consecutive days, followed by a 1-week break, with the cycle repeated throughout radiotherapy.

Most of the patients in the mupirocin group (95.6 percent) adhered to the regimen. A single patient refused treatment with mupirocin ointment, and three (3.4 percent) withdrew because of adverse effects, including pruritus with catarrhal symptoms (n=1) and nausea (n=2).