Subjective and objective effects of radioiodine therapy on the sense of smell.

Purpose: Evaluating the impact of radioiodine therapy (RIT) on olfactory function in thyroid cancer patients through quantitative and qualitative olfactory tests.

Method: In this cohort study, patients with thyroid cancer were included. Demographic, clinical, and laboratory data were collected. To subjectively evaluate the olfactory changes aftter RIT, the Visual Analog Scale (VAS), Self-Reported Mini-Olfactory Questionnaire (self-MOQ), and the University of Washington Quality of Life Questionnaire (UW-QOL) were assessed. Out of UW-QOL questions those related to saliva, taste, and overall health condition were analysed. For objective assessment, patients underwent both the Butanol Threshold Test (BTT) and the a version of Smell Identification Test (SIT). Patients were assessed before, one month, and six months after RIT.

Results: Ninety eight patients were included (Male = 17). A statistically significant decrement was observed in olfaction based on the VAS, between the baseline and one (pvalue = 0.015) and six months (pvalue = 0.031) of follow-up. Additionally, saliva (pvalue = 0.001), taste (pvalue = 0.000), and overall health condition (pvalue = 0.010) significantly decreased one-month after RIT. The measures were not different between the baseline and 6-month follow up and the improvement of index of taste was significant from 1-month to 6-months follow ups (pvalue = 0.000). However, none of the objective tests (the BTT and the SIT) indicated a significant decline in olfaction during the follow up.

Conclusion: A subjective RIT related decrease in smell function, taste, and saliva production was documented without any objective olfactory dysfunction.