Elsevier

Auris Nasus Larynx

Volume 41, Issue 5, October 2014, Pages 436-440
Auris Nasus Larynx

Olfactory bulb volume and olfactory function after radiotherapy in patients with nasopharyngeal cancer

https://doi.org/10.1016/j.anl.2014.02.004Get rights and content

Abstract

Objective

Radiotherapy is the primary method of treatment for nasopharyngeal cancer (NPC) and many side effects were reported in patients receiving radiation to this area. This study was conducted to evaluate the long-term effects of radiotherapy following NPC on olfactory bulb (OB) volume and olfactory function.

Methods

Twenty-four patients with NPC who received radiotherapy at least 12 months ago were recruited. Fourteen healthy subjects with similar demographical characteristics were recruited as the healthy control group. All volunteers were subjected to a nasoendoscopical examination, and abnormalities that could potentially cause olfactory dysfunction were the exclusion criteria from the study. An experienced radiologist segmented the MRI coronal, axial and sagittal slices manually for three-dimensional OB volume measurement in a blinded manner. Olfactory function was assessed using the Connecticut Chemosensory Clinical Research Center (CCCRC) test, and average score (0: worst, 7: best) was calculated as the total CCCRC olfactory score.

Results

The mean CCCRC score was 5.5 ± 1.1 for the nasopharyngeal cancer patients, whereas the mean score of healthy control group was 6.4 ± 0.4. There was a significant difference in the olfactory scores (p = 0.003). The mean OB volume in the NPC group was 46.7 ± 12.1 mm3. Among the patients with NPC, the cisplatin receiving group had a mean OB volume of 47.2 mm3, whereas the cisplatin + docetaxel receiving group had a mean OB volume of 46.5 mm3, and they were similar. The MRI measurement of the healthy control group was 58.6 ± 13.8 mm3. The OB volumes of the healthy control group were significantly higher (p < 0.05).

Conclusion

Radiotherapy following nasopharyngeal cancer results in a diminished OB volume and deteriorated olfactory function. Chemosensory olfactory dysfunction might be a contributing factor to lack of appetite, cancer cachexia and consequent lowered quality of life in NPC patients.

Introduction

Radiotherapy (RT) is the primary method of treatment for all types of nasopharyngeal cancer (NPC). RT to the head and neck region can result in serious consequences because important tissues are often included in the field of irradiation [1], [2], [3], [4]. Dental problems, xerostomia, gustatory dysfunction and mucositis eventually contribute to poor nutritional status and cancer cachexia and consequently lead to low quality of life in patients [5], [6], [7], [8].

The olfactory nerve is purely sensory and is specialized for the sense of smell. The olfactory system is connected to the cortical olfactory area, also known as the rhinencephalon, via olfactory nerve endings and the olfactory bulb and tract. Afferent nerve endings are situated in the olfactory epithelium and olfactory bulb (OB) and are primarily responsible for the plasticity of the olfactory system [5], [6], [7], [8], [9].

RT used in the treatment of NPC, apart from other head and neck tumors, is directed and focused especially to the region of nasal mucosa, receptor cells and nerve endings in the olfactory bulb. This study was conducted to evaluate the long-term side effects of radiotherapy on the olfactory bulb and olfactory function in NPC patients.

Section snippets

Materials and methods

This study was performed with the approval of the local ethics committee following the National Health and Medical Research guidelines and in accordance with the Declaration of Helsinki. All volunteers were provided information about the procedures, and written informed consents were obtained from them before participating in the study.

Results

The mean age of the NPC group was 48.7 ± 11.4 years; 10 were women (43.5%) and 14 were men (56.5%). Mean age of the healthy control group was 48.8 ± 7.0 years; nine were women (64.3%) and five were men (35.7%). There was no statistical significance in terms of age between the two groups. Olfactory tests and MRI scans were carried out 66.0 ± 48.6 (range, 14–218) months (mean ± SD) following the conclusion of radiotherapy and chemotherapy in the NPC group.

Discussion

Olfactory dysfunction, similar to hearing loss, can be either conductive or sensorineural in nature. Conductive dysfunction can be the result of septum deviation, nasal polyposis or iatrogenic stenosis following septum surgery. Sensorineural olfactory dysfunction is due to defects in the olfactory nerve fibers, receptors, olfactory bulb and orbitofrontal cortex. The participants in our study underwent a detailed nasoendoscopical examination and therefore conductive etiology was discarded at the

Conclusion

This study was the first to examine the long-term side effects of RT on olfactory dysfunction and olfactory bulb. Radiotherapy following nasopharyngeal cancer results in diminished OB volume and olfactory dysfunction in the long term. Diminished chemosensory olfactory dysfunction might be an aggravating factor of quality of life in NPC patients.

Authors’ contributions

Bayram Veyseller: Idea, analysis and interpretation of data, and writing the manuscript. Berke Ozucer: Patient follow-up, collecting data, and writing the manuscript. Nazan Değirmenci: Patient follow-up and collecting data. Defne Gürbüz: Radiological assessment. Makbule Tambaş, Musa Altun: Patient follow-up and oncological assessment. Fadullah Aksoy, Orhan Ozturan: Supervisors.

Funding

Bezmialem Vakif University, Scientific Research Project Unit Sponsorship.

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