Olfactory Sensations During Proton and Photon Radiotherapy: A Multicenter Prospective Observational Study

Area of Science:

• Oncology
• Radiation Oncology
• Medical Physics

Background:

• Patients undergoing radiation therapy (RT) sometimes report olfactory sensations.
• The characteristics and contributing factors of these smell events are not fully understood.

Purpose of the Study:

• To investigate the occurrence and nature of smell sensations during photon RT and proton beam therapy (PBT).
• To identify factors associated with smell perception during RT.

Main Methods:

• Prospective study of adult patients undergoing photon RT or PBT between January 2019 and August 2020.
• Weekly checklists recorded smell presence, odor type, intensity, and timing.
• Exclusion criteria included communication difficulties and pre-existing olfactory abnormalities.

Main Results:

• Smell was reported by 8.2% of 620 patients (649 courses).
• Nasal cavity radiation dose, younger age, and photon RT were significantly associated with smell perception.
• Smell incidence increased with higher nasal cavity dose (4.5% with no irradiation to 27.9% with 60%-100% isodose).
• Photon RT (10.4%) resulted in more smell reports than PBT (3.9%).
• The most common smell reported was 'burnt' (63%).

Conclusions:

• Olfactory sensations are a notable phenomenon during RT.
• Nasal cavity radiation dose, patient age, and RT modality (photon vs. proton) are key factors influencing smell perception.
• These findings aid in understanding patient-reported symptoms during RT.