FDG-PET Assessment of the Effect of Head and Neck Radiotherapy on Parotid Gland Glucose Metabolism

• Published in: International journal of radiation oncology, biology, physics Vol. 82; no. 1; pp. 321 - 326
• Main Authors: Roach, Michael C., B.E, Turkington, Timothy G., Ph.D, Higgins, Kristin A., M.D, Hawk, Thomas C., B.S, Hoang, Jenny K., MBBS, Brizel, David M., M.D
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 2012; Elsevier
• Subjects: Adult; ADULTS; Aged; Antineoplastic Agents - therapeutic use; Biological and medical sciences; Carcinoma, Squamous Cell - drug therapy; Carcinoma, Squamous Cell - radiotherapy; CARCINOMAS; Dose-Response Relationship, Radiation; Dose–volume effects; Female; FLUORINE 18; FLUORODEOXYGLUCOSE; Fluorodeoxyglucose F18 - pharmacokinetics; GLUCOSE; Glucose - metabolism; HEAD; Head and neck cancer; Head and Neck Neoplasms - drug therapy; Head and Neck Neoplasms - radiotherapy; Hematology, Oncology and Palliative Medicine; Humans; IMRT; INTERFACES; Male; Medical sciences; METABOLISM; Middle Aged; NECK; Organ Size - radiation effects; Otorhinolaryngology (head neck, general aspects and miscellaneous); Otorhinolaryngology. Stomatology; Parotid; Parotid Gland - diagnostic imaging; Parotid Gland - metabolism; Parotid Gland - radiation effects; PATIENTS; PET; PHYSIOLOGY; PLANNING; POSITRON COMPUTED TOMOGRAPHY; Positron-Emission Tomography - methods; RADIATION DOSES; Radiography; Radiology; RADIOLOGY AND NUCLEAR MEDICINE; Radiopharmaceuticals - pharmacokinetics; RADIOTHERAPY; Radiotherapy, Intensity-Modulated - methods; Retrospective Studies; SALIVA; SALIVARY GLANDS; Tumors; Head and neck cancer; Parotid; IMRT; Dose–volume effects; PET; Radionuclide study; 2-deoxy-2-fluoroglucose; Parotid gland; Fludeoxyglucose (18F); Malignant tumor; Glucose; Metabolism; Intensity modulated radiotherapy; Cancerology; Treatment; Dose―volume effects; Head and neck; ENT disease; Dose; Positron emission tomography; Cancer; Emission tomography
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/j.ijrobp.2010.08.055

Purpose Functional imaging with [F-18]-fluorodeoxyglucose positron emission tomography (FDG-PET) provides the opportunity to define the physiology of the major salivary glands before and after radiation therapy. The goal of this retrospective study was to identify the radiation dose–response relationship of parotid gland glucose metabolism in patients with head and neck squamous cell carcinoma (HNSCC). Materials and Methods Forty-nine adults with HNSCC were identified who had curative intent intensity-modulated radiation therapy (IMRT) and FDG-PET imaging before and after treatment. Using a graphical user interface, contours were delineated for the parotid glands on axial CT slices while all authors were blinded to paired PET slices. Average and maximal standard uptake values (SUV) were measured within these anatomic regions. Changes in SUV and volume after radiation therapy were correlated with parotid gland dose–volume histograms from IMRT plans. Results The average parotid gland volume was 30.7 mL and contracted 3.9 ± 1.9% with every increase of 10 Gy in mean dose ( p = 0.04). However, within the first 3 months after treatment, there was a uniform reduction of 16.5% ± 7.3% regardless of dose. The average SUVmean of the glands was 1.63 ± 0.48 pretreatment and declined by 5.2% ± 2.5% for every increase of 10 Gy in mean dose ( p = 0.04). The average SUVmax was 4.07 ± 2.85 pretreatment and decreased in a sigmoid manner with mean dose. A threshold of 32 Gy for mean dose existed, after which SUVmax declined rapidly. Conclusion Radiation dose responses of the parotid glands can be measured by integrated CT/FDG-PET scans. Retrospective analysis showed sigmoidal declines in the maximum metabolism but linear declines in the average metabolism of the glands with dose. Future studies should correlate this decline in FDG uptake with saliva production to improve treatment planning.