Olfactory bulb volume and olfactory function after radiotherapy in patients with nasopharyngeal cancer
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.
References (23)
- et al.
De Gustibus: time scale of loss and recovery of tastes caused by radiotherapy
Radiother Oncol
(2002) - et al.
Change in olfaction after radiotherapy for nasopharyngeal cancer—a prospective study
Am J Otolaryngol
(2002) - et al.
Effects of radiotherapy on olfactory function
Radiother Oncol
(2005) - et al.
Retrospective analysis of nasopharyngeal carcinoma treated during 1976–1985: late complications following megavoltage irradiation
Br J Radiol
(1992) - et al.
Vocal cord palsy: possible late complication of radiotherapy for head and neck cancer
Ann Otol Rhinol Laryngol
(1995) - et al.
Radiation induced cranial nerve palsy: hypoglossal nerve and vocal cord palsies
J Laryngol Otol
(1991) - et al.
Bilateral vocal cord paralysis following radiation therapy for nasopharyngeal carcinoma
J Otorhinolaryngol Relat Spec
(1995) Gustatory tissue injury in man: radiation dose response relationships and mechanisms of taste loss
Br J Cancer Suppl
(1986)Taste and smell losses in normal aging and disease
J Am Med Assoc
(1997)- et al.
Characteristics of olfactory disorders in relation to major causes of olfactory loss
Arch Otolaryngol Head Neck Surg
(2002)
Olfactory processing in a changing brain
Neuroreport
Cited by (22)
Changes in brain gray matter volume in nasopharyngeal carcinoma patients after radiotherapy in long-term follow-up
2023, Brazilian Journal of OtorhinolaryngologyA multidimensional cohort study of late toxicity after intensity modulated radiotherapy for sinonasal cancer
2020, Radiotherapy and OncologyA systematic review of smell alterations after radiotherapy for head and neck cancer
2017, Cancer Treatment ReviewsCitation Excerpt :Thirteen studies were prospective [46,48,51,53–62], eight were cross-sectional [47,50,52,63–67] and two were retrospective [49,68] (Table 2). Treatment included RT-only in seven studies [53–55,58,59,66,68], surgery and RT in five studies [50,51,57,67], CRT in six studies [46–48,52,56], trimodal therapy with chemotherapy, surgery and RT in four studies [49,60] and electrochemotherapy and RT in one study [62]. Six studies collected information on factors that can affect olfaction in addition to RT such as nasal blockage [48], nasal flow [46], compromised neurological status [54], previous trauma [47,57], severe infection [57] or comorbidities known to affect olfactory function [60].
Neurosensory, aesthetic and dental late effects of childhood cancer therapy
2015, Bulletin du CancerEffects of radiotherapy on olfaction and nasal function in head and neck cancer patients
2020, American Journal of Otolaryngology - Head and Neck Medicine and SurgeryCitation Excerpt :Veysellar et al. looked at nasopharyngeal cancer patients treated with radiotherapy and reported that the olfactory bulb volumes on MRI scan and olfactory threshold were significantly diminished in patients as compared to healthy controls. This was attributed to the direct radiation induced damage to the olfactory mucosa or olfactory bulb and other olfactory centers [8]. However these harmful effects on olfaction were not as pronounced in a study by Wang et al. where 75.6% of patients retained normal olfactory function after IMRT for nasopharyngeal carcinoma [9].
Current status of sinonasal cancer survivorship care
2023, Head and Neck