Association of nasal irrigation with reduced nasal symptoms after radioiodine ablation in differentiated thyroid cancer: a retrospective cohort study with propensity score matching.

Background: Nasal symptoms after radioactive iodine (RAI) therapy in differentiated thyroid cancer have received less attention than salivary or lacrimal toxicity. Nasal saline irrigation is a simple supportive-care measure, but its association with post-RAI nasal symptom burden remains insufficiently evaluated. Methods: This single-center retrospective cohort study included patients with differentiated thyroid cancer who received Results: Among 185 eligible patients, 92 received standard care and 93 received nasal irrigation. After matching, 148 patients were included in the primary analysis. Symptoms meeting the prespecified VAS ≥3 threshold occurred in 27 of 74 patients (36.5%) in the standard-care group and 13 of 74 patients (17.6%) in the irrigation group (risk difference, -20.27 percentage points; 95% CI, -34.32 to -6.22; P = 0.005). Rescue medication was required in 25 of 74 patients (33.8%) and 11 of 74 patients (14.9%), respectively. Nasal dryness showed the most consistent between-group difference. The day-7 T/B ratio was lower in the irrigation group (2.24 ± 0.76 vs. 2.56 ± 0.81; P = 0.012), whereas the day-3 ratio was similar. Conclusions: In this retrospective cohort, stepped nasal saline irrigation was associated with fewer early post-RAI nasal symptoms and less rescue medication use. The imaging findings were exploratory and should not be interpreted as direct evidence of enhanced radioiodine clearance. Prospective studies are needed to confirm these findings.