Quantitative measurements of radiation‐induced fibrosis for head and neck cancer: A narrative review

Abstract Objectives To provide a comprehensive summary of the different modalities available to measure soft tissue fibrosis after radiotherapy in head and neck cancer patients. Data Sources PubMed, Scopus, and Web of Sciences. Review Methods A search was conducted using a list of medical subject headings and terms related to head and neck oncology, radiation fibrosis, and quantitative measurements, including bioimpedance, MRI, and ultrasound. Original research related to quantitative measurement of neck fibrosis post‐radiotherapy was included without time constraints, while reviews, case reports, non‐English texts, and inaccessible studies were excluded. Discrepancies during the review were resolved by discussing with the senior author until consensus was reached. Results A total of 284 articles were identified and underwent title and abstract screening. Seventeen articles had met our criteria for full‐text review based on relevance, of which nine had met our inclusion criteria. Young's modulus (YM) and viscoelasticity measures have demonstrated efficacy in quantifying neck fibrosis, with fibrotic tissues displaying significantly higher YM values and altered viscoelastic properties such as increased stiffness rate‐sensitivity and prolonged stress‐relaxation post‐radiation. Intravoxel incoherent motion offers detailed insights into tissue changes by assessing the diffusion of water molecules and blood perfusion, thereby differentiating fibrosed from healthy tissues. Shear wave elastography has proven to be an effective technique for quantifying radiation‐induced fibrosis in the head and neck region by measuring shear wave velocity. Conclusion There are various modalities to measure radiation‐induced fibrosis, each with its unique strengths and limitations. Providers should be aware of these implications and decide on methodologies based on their specific clinical workflow. Level of Evidence Step 5.