Olfactory change after intensity-modulated radiotherapy for nasopharyngeal carcinoma

Radiotherapy is the mainstay of treatment for nasopharyngeal cancer (NPC), but many side effects were reported in NPC patients receiving radiotherapy. This study was conducted to evaluate the long-term effects of intensity-modulated radiotherapy (IMRT) on olfactory function.

The olfactory function of 41 NPC patients was assessed by a traditional Chinese version of the University of Pennsylvania Smell Identification Test (UPSIT-TC). The patients also filled out a Taiwanese version of the 22-item Sino-Nasal Outcome Test (TWSNOT-22) questionnaire and received imaging examinations of the sinuses before IMRT and 1 year after IMRT. The sinus imaging was scored according to the Lund-Mackay system.

The mean UPSIT-TC scores were 30.6 before IMRT and 28.0 after IMRT and the decrease in UPSIT-TC scores was significant (p = 0.001). The mean TWSNOT-22 scores were 32.1 before IMRT and 28.8 after IMRT. The change in TWSNOT-22 scores was not significant, but the scores for item 5 "loss of smell or taste" significantly increased after IMRT (p = 0.035). The mean total computed tomography (CT) scores were 1.7 before IMRT and 3.2 after IMRT, and the mean ethmoid CT scores were 0.5 before IMRT and 1.2 after IMRT. The increase in total CT and ethmoid CT scores was both significant (p = 0.004 and 0.002). The decrease in UPSIT-TC scores was moderately negatively correlated with the increase in total CT and ethmoid CT scores (r = -0.348 and -0.423).

Our results showed that the olfactory function of NPC patients was mildly impaired after IMRT, which can cause rhinosinusitis.