Effects of radiotherapy on olfactory function in patients with head and neck cancer
| ISRCTN | ISRCTN14947812 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN14947812 |
| ClinicalTrials.gov (NCT) | Nil known |
| Clinical Trials Information System (CTIS) | Nil known |
| Protocol serial number | Funding grant number CMRPG6L0041-3 |
| Sponsor | Chang Gung Memorial Hospital |
| Funder | Chang Gung Medical Foundation |
- Submission date
- 28/09/2025
- Registration date
- 29/09/2025
- Last edited
- 29/09/2025
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Cancer
Plain English summary of protocol
Background and study aims
Head and neck cancer patients often receive radiotherapy as part of their treatment. While radiotherapy is effective in controlling cancer, it can also affect nearby structures, including the olfactory system. Loss of smell may reduce quality of life, but little is known about how radiotherapy dose to the olfactory region relates to long-term changes in smell function. This study aims to determine how many patients developed olfactory dysfunction after radiotherapy, and whether higher radiation doses were associated with a greater risk of smell loss. Secondary analyses explore changes in the Taiwan Smell Identification Test (TWSIT), a standardised smell test, scores over time, dose-response relationships, and potential threshold doses predictive of olfactory dysfunction.
Who can participate?
Adult patients with head and neck cancer who were scheduled for intensity-modulated radiotherapy (IMRT) at Chang Gung Memorial Hospital, Chiayi, Taiwan.
What does the study involve?
Participants were prospectively enrolled between January 2021 and December 2023. All participants completed the TWSIT, a standardised smell test, before treatment and again after radiotherapy at 1, 3, 6, and 12 months. Radiation dose to the olfactory structures was measured from radiotherapy treatment plans.
What are the possible benefits and risks of participating?
By clarifying the relationship between radiation dose and olfactory outcomes, this study may help doctors to better predict, explain, and potentially reduce smell-related side effects of head and neck cancer treatment in the future.
No risks provided at registration
Where is the study run from?
Chang Gung Memorial Hospital, Chiayi, Taiwan.
When is the study starting and how long is it expected to run for?
November 2020 to December 2023
Who is funding the study?
Chang Gung Medical Foundation, Taiwan.
Who is the main contact?
Dr Geng He Chang, genghechang@gmail.com
Contact information
Public, Scientific, Principal investigator
No.8, W. Sec., Jiapu RD., Puzi City
Chiayi
61363
Taiwan
 ORCID ID |
0000-0001-5939-9747 |
|---|---|
| Phone | +886-5-3621000 ext.2076 |
| genghechang@gmail.com |
Study information
| Primary study design | Observational |
|---|---|
| Study design | Prospective observational cohort study single-centre study |
| Secondary study design | Cohort study |
| Study type | Participant information sheet |
| Scientific title | Prospective observational cohort study of radiotherapy dose to the olfactory region and subsequent olfactory dysfunction in head and neck cancer patients at Chang Gung Memorial Hospital |
| Study acronym | OLFACT-RT |
| Study objectives | To investigate the relationship between radiation dose delivered to the olfactory region and the occurrence of olfactory dysfunction in patients with head and neck cancer receiving intensity-modulated radiotherapy (IMRT). |
| Ethics approval(s) |
Approved 27/11/2020, Chang Gung Medical Foundation Institutional Review Board (199 Tung Hwa North Road, Taipei, 10507, Taiwan; +886-3-3196200 ext.3705; tsengshui@cgmh.org.tw), ref: 202001923B0C501 |
| Health condition(s) or problem(s) studied | Head and neck cancers (including nasopharyngeal carcinoma, nasal cavity cancer, oral cavity cancer, tonsil cancer, hypopharyngeal cancer, laryngeal cancer, parotid cancer and palate cancer) |
| Intervention | All participants received standard-of-care intensity-modulated radiotherapy (IMRT), with some patients also receiving concurrent chemotherapy as clinically indicated. No additional interventions were assigned by the investigators. |
| Intervention type | Procedure/Surgery |
| Primary outcome measure(s) | The proportion of participants with olfactory dysfunction (TWSIT <40) measured using the Taiwan Smell Identification Test (TWSIT, score range 0–48) at baseline (pre-RT), end of radiotherapy, and at 1, 3, 6, and 12 months post-RT |
| Key secondary outcome measure(s) | 1. Change in olfactory function measured using the change in TWSIT scores (continuous 0–48) from baseline to end of RT and to 1, 3, 6, and 12 months post-RT 2. Dose–response relationship measured using the association between mean olfactory-region radiation dose (Gy) and change in TWSIT scores measured using radiotherapy treatment plans at one timepoint 3. Dose threshold exploration measured using the identification of potential radiation dose cut-off values predictive of olfactory dysfunction using ROC analysis, measured using radiotherapy treatment plans at one timepoint 4. Regression analysis of odds measured using the logistic regression analysis of odds of post-RT olfactory dysfunction in relation to olfactory-region dose, adjusted for relevant covariates measured using radiotherapy treatment plans at one timepoint |
| Completion date | 31/12/2023 |
Eligibility
| Participant type(s) | Patient |
|---|---|
| Age group | Mixed |
| Lower age limit | 18 Years |
| Upper age limit | 100 Years |
| Sex | All |
| Target sample size at registration | 99 |
| Total final enrolment | 63 |
| Key inclusion criteria | 1. Patients with histologically confirmed head and neck cancer scheduled for curative intensity modulated radiotherapy (IMRT) at Chang Gung Memorial Hospital 2. Provided written informed consent approved by the Chang Gung Medical Foundation IRB |
| Key exclusion criteria | 1. Severe nasal septal deviation with hypertrophic turbinate 2. Chronic rhinosinusitis with or without nasal polyps 3. History of head trauma 4. Prior radiotherapy to the head and neck region 5. Baseline olfactory dysfunction defined as Taiwan Smell Identification Test (TWSIT) score <40 |
| Date of first enrolment | 12/01/2021 |
| Date of final enrolment | 17/11/2023 |
Locations
Countries of recruitment
- Taiwan
Study participating centre
Chiayi
61363
Taiwan
Results and Publications
| Individual participant data (IPD) Intention to share | Yes |
|---|---|
| IPD sharing plan summary | Published as a supplement to the results publication |
| IPD sharing plan | The datasets generated and/or analysed during the current study will be published as a supplement to the results publication. Individual participant data (IPD) will not be shared due to ethical and privacy restrictions. Only aggregated results will be reported in publications and presentations. |
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Participant information sheet | Participant information sheet | 11/11/2025 | 11/11/2025 | No | Yes |
| Study website | Study website | 11/11/2025 | 11/11/2025 | No | Yes |
Editorial Notes
29/09/2025: Study's existence confirmed by the Chang Gung Medical Foundation Institutional Review Board, Taiwan.
