Assessment of Olfactory Threshold in Patients Undergoing Radiotherapy for Head and Neck Malignancies

Document Type : Original


1 Department of Otorhinolaryngology, Nose and Sinus Diseases Research Center, Guilan University of Medical Sciences, Rasht, Iran.

2 Department of Radiotherapy, Razi Hospital, Guilan University of Medical Sciences, Guilan, Iran.


Radiotherapy is a common treatment modality for patients with head and neck malignancies. As the nose lies within the field of radiotherapy of the head and neck, the olfactory fibers and olfactory receptors may be affected by radiation. The aim of this study was to evaluate changes in olfactory threshold in patients with head and neck malignancies who have received radiation to the head and neck.
Materials and Methods:
The olfactory threshold of patients with head and neck malignancies was assessed prospectively before radiation therapy and serially for up to 6 months after radiotherapy using sniff bottles. In vivo dosimetry was performed using 82 LiF (MCP) chips and a thermoluminescent dosimeter (TLD) system.
Sixty-one patients were recruited before radiotherapy was commenced. Seven patients did not return for evaluation after radiation. Fifty-four patients were available for follow-up assessment (28 women, 26 men; age, 22–86 years; median, 49 years). Total radiation dose was 50.1 Gy (range, 30–66 Gy). Mean olfactory threshold scores were found to deteriorate significantly at various timepoints after radiotherapy (11.7 before radiotherapy versus 4.0 at Month 6, general linear model, P<0.0001). With in vivo dosimetry, we found that the median measured dose to the olfactory area was 334 µC. We also identified a cutoff point according to the dose to the olfactory epithelium. Olfactory threshold was significantly decreased 2–6 weeks after initiation of therapy, with cumulative local radiation >135 µC (Mann-Whitney U test, P=0.01).
Deterioration in olfactory threshold scores was found at 6 months after initiation of radiation therapy. Provided that these results are reproducible, an evaluation of olfactory functioning in patients with head and neck malignancies using in vivo dosimetry may be useful for determining the optimal dose for patients treated with conformal radiotherapy techniques while avoiding the side effects of radiation.


Main Subjects

1. Sagar SM, Thomas RJ, Loverock LT, Spittle MF. Olfactory sensations produced by high-energy photon irradiation of the olfactory receptor mucosa in humans. International journal of radiation oncology, biology, physics 1991;20(4):771-6.
 2. Lee AW, Law SC, Ng S, Chan DK, Poon Y, Foo W, et al. Retrospective analysis of nasopharyngeal carcinoma treated during 1976–1985: late complications following megavoltage irradiation. British journal of radiology 1992;65(778):918-28.
 3. Temmel AF, Quint C, Schickinger-Fischer B, Klimek L, Stoller E, Hummel T. Characteristics of olfactory disorders in relation to major causes of olfactory loss. Archives of Otolaryngology-Head and Neck Surgery 2002; 128(6):635.
 4. Ophir D, Guterman A, Gross-Isseroff R. Changes in smell acuity induced by radiation exposure of the olfactory mucosa. Archives of otolaryngology--head  neck surgery 1988; 114 (8): 853-5.
 5. Ho W-k, Kwong DL, Wei WI, Sham JS. Change in olfaction after radiotherapy for nasopharyngeal cancer-A prospective study. American journal of otolaryngology 2002;23(4):209-14.
 6. Hua MS, Chen ST, Tang LM, Leung WM. Olfactory function in patients with nasopharygeal carcinoma following radiotherapy. Brain Injury 1999;13(11):905-15.
7. Hölscher T, Seibt A, Appold S, Dörr W, Herrmann T, Hüttenbrink KB, et al. Effects of radiotherapy on olfactory function. Radiotherapy and oncology 2005;77(2):157-63.
8. Doty RL, McKeown DA, Lee WW, Shaman P. A study of the test-retest reliability of ten olfactory tests. Chem Senses 1995; 20(6):645-56.
9. Hummel T, Sekinger B, Wolf S, Pauli E, Kobal G. ‘Sniffin’Sticks': Olfactory Performance Assessed by the Combined Testing of Odor Identification, Odor Discrimination and Olfactory Threshold. Chemical senses 1997;22(1):39-52.
Kobal G, Klimek L, Wolfensberger M, Gudziol H, Temmel A, Owen CM, et al. Multicenter investigation of 1,036 subjects using a standardized method for the assessment of olfactory function combining tests of odor identification, odor discrimination, and olfactory thresholds. European archives of oto-rhino-laryngology: official journal of the European Federation of Oto-Rhino-Laryngological Societies 2000; 257(4):205-11.
11. Moghaddam BG, Vahabi-Moghaddam M, Sadremomtaz A. Evaluation of target dose based on water-equivalent thickness in external beam radiotherapy. Journal of medical physics/ Association of Medical Physicists of India 2013; 38(1):44-51.
12. Prevention of accidental exposures to patients undergoing radiation therapy. A report of the International Commission on Radiological Protection. Annals of the ICRP 2000; 30(3):7-70.
13. Schaupp H, Krull R. Radiogenic disorder in sense of smell (author's transl). Laryngologie, Rhinologie, Otologie 1975; 54(4):340.
14. Qiu Q, Chen S, Meng C, Liao F, Huang X,Li T. Observation on the changes in nasopharyngeal carcinoma patients' olfactory before and after radiotherapy].Lin chuang er bi yan hou ke za zhi= Journal of clinical otorhinolaryngology 2001;           15(2): 57.
15. Bramerson A, Nyman J, Nordin S, Bende M. Olfactory loss after head and neck cancer radiation therapy. Rhinology. 2013; 51(3):206-9.
16. Leyrer CM, Chan MD, Peiffer AM, Horne E, Harmon M, Carter AF, et al. Taste and smell disturbances after brain irradiation: A dose–volume histogram analysis of a prospective observational study. Practical Radiation Oncology. 2013.
17. Landis BN, Hummel T, Hugentobler M, Giger R, Lacroix JS. Ratings of overall olfactory function. Chem Senses. 2003;28(8):691-4.
18. Landis B, Hummel T, Lacroix J-S. Basic and clinical aspects of olfaction. Advances and technical standards in neurosurgery: Springer; 2005. p. 69-105.