Mid-treatment 18F-FDG PET imaging changes in parotid gland correlates to radiation-induced xerostomia

• Published in: Radiotherapy and oncology Vol. 186; p. 109745
• Main Authors: Trada, Yuvnik, Lee, Mark T., Jameson, Michael G., Chlap, Phillip, Keall, Paul, Moses, Daniel, Lin, Peter, Fowler, Allan
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.09.2023
• Subjects: FDG-PET; Head and Neck Neoplasm; Mid-treatment; Prediction; Radiotherapy; Xerostomia; FDG-PET; Head and Neck Neoplasm; Radiotherapy; Xerostomia; Mid-treatment; Prediction
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2023.109745

•We present results of prospective mid-treatment FDG-PET imaging biomarker study for xerostomia prediction.•56 mucosal head and neck patients treated with definitive radiotherapy were evaluated with FDG-PET imaging at baseline and week 3 mid-radiotherapy.•We found early metabolic changes in the parotid gland improved prediction of subsequent risk of xerostomia.•There is a potential for FDG-PET changes in parotid gland to be utilised in future adaptive radiotherapy trials for toxicity minimisation. The aim of this study was to measure functional changes in parotid glands using mid-treatment FDG-PET/CT and correlate early imaging changes to subsequent xerostomia in mucosal head and neck squamous cell carcinoma patients undergoing radiotherapy. 56 patients from two prospective imaging biomarker studies underwent FDG-PET/CT at baseline and during radiotherapy (week 3). Both parotid glands were volumetrically delineated at each time point. PET parameter SUVmedian were calculated for ipsilateral and contralateral parotid glands. Absolute and relative change (Δ) in SUVmedian were correlated to moderate-severe xerostomia (CTCAE grade ≥ 2) at 6 months. Four predictive models were subsequently created using multivariate logistic regression using clinical and radiotherapy planning parameters. Model performance was calculated using ROC analysis and compared using Akaike information criterion (AIC) 29 patients (51.8%) developed grade ≥ 2 xerostomia. Compared to baseline, there was an increase in SUVmedian at week 3 in ipsilateral (8.4%) and contralateral (5.5%) parotid glands. Increase in ipsilateral parotid Δ SUVmedian (p = 0.04) and contralateral mean parotid dose (p = 0.04) were correlated to xerostomia. The reference ‘clinical’ model correlated to xerostomia (AUC 0.667, AIC 70.9). Addition of ipsilateral parotid Δ SUVmedian to the clinical model resulted in the highest correlation to xerostomia (AUC 0.777, AIC 65.4). Our study shows functional changes occurring in the parotid gland early during radiotherapy. We demonstrate that integration of baseline and mid-treatment FDG-PET/CT changes in the parotid gland with clinical factors has the potential to improve xerostomia risk prediction which could be utilised for personalised head and neck radiotherapy.