Metabolic imaging biomarkers of postradiotherapy xerostomia.
OBJECTIVE
Xerostomia is a major complication of head and neck radiotherapy (RT). Available xerostomia measures remain flawed. [(18)F]fluorodeoxyglucose-labeled positron emission tomography-computed tomography (FDG-PET-CT) is routinely used for staging and response assessment of head and neck cancer. We investigated quantitative measurement of parotid gland FDG uptake as a potential biomarker for post-RT xerostomia.


METHODS
Ninety-eight locally advanced head and neck cancer patients receiving definitive RT underwent baseline and post-RT FDG-PET-CT on a prospective imaging trial. A separate validation cohort of 14 patients underwent identical imaging while prospectively enrolled in a second trial collecting sialometry and patient-reported outcomes. Radiation dose and pre- and post-RT standard uptake values (SUVs) for all voxels contained within parotid gland ROI were deformably registered.


RESULTS
Average whole-gland or voxel-by-voxel models incorporating parotid D(Met) (defined as the pretreatment parotid SUV weighted by dose) accurately predicted posttreatment changes in parotid FDG uptake (e.g., fractional parotid SUV). Fractional loss of parotid FDG uptake closely paralleled early parotid toxicity defined by posttreatment salivary output (p < 0.01) and Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer xerostomia scores (p < 0.01).


CONCLUSIONS
In this pilot series, loss of parotid FDG uptake was strongly associated with acute clinical post-RT parotid toxicity. D(Met) may potentially be used to guide function-sparing treatment planning. Prospective validation of FDG-PET-CT as a convenient, quantifiable imaging biomarker of parotid function is warranted and ongoing.
Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA.
Blake
B
Cannon
David L
DL
Schwartz
Lei
L
Dong
D000328:Adult; D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007012:Hypopharyngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy; D007822:Laryngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects; D009959:Oropharyngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy; D010306:Parotid Gland / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000528:radiation effects; D010865:Pilot Projects; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D011832:Radiation Injuries / Q000000981:diagnostic imaging / Q000378:metabolism; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011879:Radiotherapy Dosage; D014057:Tomography, X-Ray Computed; D014987:Xerostomia / Q000000981:diagnostic imaging* / Q000209:etiology / Q000378:metabolism
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18