18 FDG positron emission tomography mining for metabolic imaging biomarkers of radiation-induced xerostomia in patients with oropharyngeal cancer

• Published in: Clinical and translational radiation oncology Vol. 29; p. 93
• Main Authors: Elhalawani, Hesham, Cardenas, Carlos E, Volpe, Stefania, Barua, Souptik, Stieb, Sonja, Rock, Calvin B, Lin, Timothy, Yang, Pei, Wu, Haijun, Zaveri, Jhankruti, Elgohari, Baher, Abdallah, Lamiaa E, Jethanandani, Amit, Mohamed, Abdallah S R, Court, Laurence E, Hutcheson, Katherine A, Brandon Gunn, G, Rosenthal, David I, Frank, Steven J, Garden, Adam S, Rao, Arvind, Fuller, Clifton D
• Format: Journal Article
• Language: English
• Published: Ireland 01.07.2021
• Subjects: FDG-PET; Predictive model; Head and neck cancer; Imaging biomarkers; Radiotherapy; Xerostomia
• ISSN: 2405-6308

Head and neck cancers radiotherapy (RT) is associated with inevitable injury to parotid glands and subsequent xerostomia. We investigated the utility of SUV derived from FDG-PET to develop metabolic imaging biomarkers (MIBs) of RT-related parotid injury. Data for oropharyngeal cancer (OPC) patients treated with RT at our institution between 2005 and 2015 with available planning computed tomography (CT), dose grid, pre- & first post-RT FDG-PET-CT scans, and physician-reported xerostomia assessment at 3-6 months post-RT (Xero 3-6 ms) per CTCAE, was retrieved, following an IRB approval. A CT-CT deformable image co-registration followed by voxel-by-voxel resampling of pre & post-RT FDG activity and dose grid were performed. Ipsilateral (Ipsi) and contralateral (contra) parotid glands were sub-segmented based on the received dose in 5 Gy increments, i.e. 0-5 Gy, 5-10 Gy sub-volumes, etc. Median and dose-weighted SUV were extracted from whole parotid volumes and sub-volumes on pre- & post-RT PET scans, using in-house code that runs on MATLAB. Wilcoxon signed-rank and Kruskal-Wallis tests were used to test differences pre- and post-RT. 432 parotid glands, belonging to 108 OPC patients treated with RT, were sub-segmented & analyzed. Xero 3-6 ms was reported as: non-severe (78.7%) and severe (21.3%). SUV- median values were significantly reduced post-RT, irrespective of laterality (p = 0.02). A similar pattern was observed in parotid sub-volumes, especially ipsi parotid gland sub-volumes receiving doses 10-50 Gy (p < 0.05). Kruskal-Wallis test showed a significantly higher mean RT dose in the contra parotid in the patients with more severe Xero 3-6mo (p = 0.03). Multiple logistic regression showed a combined clinical-dosimetric-metabolic imaging model could predict the severity of Xero 3-6mo; AUC = 0.78 (95%CI: 0.66-0.85; p < 0.0001). We sought to quantify pre- and post-RT FDG-PET metrics of parotid glands in patients with OPC. Temporal dynamics of PET-derived metrics can potentially serve as MIBs of RT-related xerostomia in concert with clinical and dosimetric variables.