The effect of chemotherapy on olfactory function and mucociliary clearance

Olfactory sensory neurons and the olfactory mucosa are both important for optimal olfactory function. The potential nasal mucosal toxicity of chemotherapy regimens has not been assessed yet. The aim of this study was to objectively investigate the effect of chemotherapy on mucociliary clearance and olfactory function and to evaluate whether this effect differs between different chemotherapy regimens and age groups.

The study included consecutive patients admitted for the treatment of a variety of primary tumors (except head and neck and brain malignancies). Patients were evaluated for olfaction and mucociliary clearance before and immediately after completing the last session of chemotherapy cycles, according to the therapeutic protocol. For objective evaluation, the saccharine test was used for mucociliary clearance and the Sniffin’ Sticks test for olfactory function. Of the 46 initial patients, 30 completed the study. Groups were formed according to the chemotherapy regimen (four groups: CA (doxorubicin + cyclophosphamide), Folfox (oxaliplatin +5-FU + folinic acid), DCF (docetaxel + cisplatin +5-FU), and GC (gemcitabine + cisplatin)) and according to age (two groups: < 55 years and > 55 years).

In the overall analyses, significant deterioration was noted in both mucociliary clearance time and smell scores (olfactory threshold (OT), olfactory discrimination (OD), olfactory identification (OI), and the composite threshold–discrimination–identification (TDI) score). The changes in these scores showed no significant differences between chemotherapy groups. The decrease in OT and global TDI scores was more severe in the younger age group.

Chemotherapy impairs both the mucociliary clearance and olfactory function in cancer patients. This might reflect the collective negative effect of chemotherapy on olfactory function, not only through the neurocytotoxic effect but also the cytotoxic effect on the nasal mucosa. In addition, the reduction in olfactory threshold and total olfactory function scores was seen to be more profound in younger patients, which could have been due to higher initial scores.