An observational study in Glioblastoma Multiforme, Adult, Glioblastoma or Gliosarcoma and Glioblastoma, Adult, sponsored by Sied Kebir. Recruiting at 2 sites in Germany. Open to participants aged 18 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-08-24.
Sponsored by Sied Kebir · Observational
The study aims to investigate the prognostic significance of olfactory function in patients with glioblastoma. We are examining olfactory function at various points during therapy and correlating the results with survival data. In addition, neurocognitive tests will be carried out to correlate the results of olfactory function with the patient's cognitive abilities. Investigations into the quality of life and psychological condition of the patients are also performed. In addition to the cohort of glioblastoma patients, there is a control cohort without tumor disease in which the olfactory testing is also carried out in order to have a comparison.
Background: Olfactory impairment is frequent in glioblastoma and is associated with poor overall survival. However, earlier studies were limited by confounding of important predictive factors and the lack of long-term olfactory assessments to evaluate treatment-related neurotoxicity.
Aim: To determine whether olfactory function is an independent prognostic marker for survival, quality of life and neurocognitive outcome in glioblastoma.
Design: Prospective, multicenter cohort study with 64 glioblastoma patients and 64 comparable controls without tumor disease. Patients were stratified by baseline olfactory status, extent of resection, radiologic involvement of olfactory regions,O6-methylguanine DNA methyltransferase (MGMT) promoter methylation, age, and Karnofsky performance status.
Methods: Olfactory function will be serially assessed from diagnosis to treatment using Sniffin' Sticks (identification and threshold tests). Psychosocial assessments, neurocognitive testing and quality of life assessments will be performed at intervals. Coronal T2- and T1-weighted MRI scans will be evaluated independently by blinded neuroradiologists to identify olfactory involvement.
Next-generation sequencing will be used to investigate molecular correlates of hyposmia. As part of a parallel translational study, blood samples will be taken to analyze extracellular vesicles.
Olfactory testing:
In the identification test, 12 sniffin sticks are presented, which the patient has to name using a selection card with four terms each. Both nostrils are tested individually at each visit during the identification test. A correct answer scores one point. A maximum of 12 points is possible.
The threshold test consists of 16 dilution levels. Each level contains one sniffin stick with odor and two blanks. All three sniffin sticks of a dilution level are presented to the patient one after the other with eyes closed. The patient must indicate which of the three sticks contains an odor. Depending on whether the patient gives the correct answer, the three sniffin sticks in the next higher or next lower level are presented next. A maximum of 16 points is possible.
2,132 studies on the registry are indexed under Glioblastoma; 464 are open to participants now.
This study's planned enrollment of 128 is above the median of 60 across 208 observational studies indexed under Glioblastoma.
Browse Glioblastoma studies →Sied Kebir is the lead sponsor of 2 studies on the registry; 1 is open to participants now.
Counted across the registry records on this site, refreshed daily.
Newly-diagnosed glioblastoma
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A 0–100 scale of how well someone can carry out everyday activities. 100 is no complaints and no signs of illness; 70 is able to look after yourself but not to work or keep up normal activity; 50 is needing considerable help and frequent medical care.
Studies often ask for 60 or 70 and above. Your doctor gives the score.
Karnofsky performance status (KPS)
A 0–100 scale of how well someone can carry out everyday activities. 100 is no complaints and no signs of illness; 70 is able to look after yourself but not to work or keep up normal activity; 50 is needing considerable help and frequent medical care.
Studies often ask for 60 or 70 and above. Your doctor gives the score.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Diagnostic Test: olfactory testing (threshold and identification test)
Control group of patients with non-tumourous (neurological) diseases not primarily associated with an olfactory dysfunction
Diagnostic Test: olfactory testing (threshold and identification test)
In the identification test, 12 sniffin sticks are presented, which the patient has to name using a selection card with four terms each. Both nostrils are tested individually at each visit during the identification test. A correct answer scores one point. A maximum of 12 points is possible. The threshold test consists of 16 dilution levels. Each level contains one sniffin stick with odor and two blanks. All three sniffin sticks of a dilution level are presented to the patient one after the other with eyes closed. The patient must indicate which of the three sticks contains an odor. Depending on whether the patient gives the correct answer, the three sniffin sticks in the next higher or next lower level are presented next. A maximum of 16 points is possible.
Overall survival
Overall survival in relation to olfactory function
Time frame: From tumor diagnosis to death (usually 6 to 24 months)
Progression free survival
Progression free survival in relation to olfactory function
Time frame: From date of first surgery until the date of first progression (MRI)
Neurocognition
Neurocognition in relation to olfactory function The following tests are used for neurocognition testing: * Immediate and delayed story recall from the Rivermead Behavioural Memory Test * Number span (forward and backward) and block span (forward and backward) from the Wechsler Memory Scale * Phonemic word fluency from the Regensburg Word Fluency Test (phonemic) * Trail Making Test A and B
Time frame: From enrollment to 2 years after the end of radiotherapy
Quality of Life (QoL)
Quality of Life in relation to olfactory function The following questionnaires are used to assess quality of life: * EORTC QLQ-C30 (Version 3.0; Part A with 28 questions on a Likert scale, 28 to 112 points, Higher score means lower quality of life; Part B with 2 questions on a Likert scale, 2 to 14 points, Lower score means lower quality of life ) * EORTC QLQ-BN20 (20 questions on a Likert scale; 20 to 80 points; Higher score means lower quality of life)
Time frame: From enrollment to 2 years after the end of radiotherapy
Psychological condition
Psychological well-being in relation to olfactory function The following psychiatric questionnaires are used: * Patient Health Questionnaire-8 (PHQ-8): 8 questions on a Likert scale, score 0 to 24, higher score indicate more depression * Generalized Anxiety Disorder 7 (GAD-7): 7 questions on a Likert scale, score 0 to 21, higher score indicate more anxiety * National Comprehensive Cancer Network (NCCN) Distress Thermometer: Score 1 to 10, higher score indicate more distress
Time frame: From enrollment to 2 years after the end of radiotherapy
Plan to share: Yes — Clinical Data from the other study centers will be transferred pseudonymously to the study headquarters in Essen. Only pseudonymized data is also used for accompanying scientific projects.
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Sied Kebir