Logistic Regression Analysis of Clinical and Dosimetric Predictors of Post-radiation Hypothyroidism in Patients with Head and Neck Cancer

Summary: Hypothyroidism commonly occurs as a side effect following radiotherapy for head and neck cancers, yet limited information exists to predict the risk of post-radiation hypothyroidism. This study aims to investigate the clinical and dosimetric factors that may predict post-radiation hypothyroidism. A retrospective review was conducted on patients with head and neck cancer treated between 2018 and 2021, with a minimum follow-up duration of 12 months. Thyroid glands were contoured on CT scans, and dose-volume histograms were analyzed, incorporating thyroid volume and V5–60 into the analysis. Logistic regression and receiver operating characteristic (ROC) analysis were performed to identify predictors and assess the model's predictive value. Among the 84 eligible patients, 17 (20.2%) developed hypothyroidism within one year. The percentage of thyroid volume received 30 Gy (V30) emerged as the sole significant dosimetric predictor of post-radiation hypothyroidism (odds ratio [OR] 1.02, CI95% 1.005–1.05, p = 0.03). Univariable analysis revealed significant differences in cancer histopathology, primary tumor site, V15, V30, VS15 and VS30 between the hypothyroid and normal groups (p < 0.10). Multivariable analysis identified primary cancer site (OR 9.09, CI95%: 1.59–100) and V30 (OR 1.26, CI95% 1.007–1.76) as independent significant variables. The predictive model incorporating cancer histopathology, primary tumor site, V15,30, and VS15,30 effectively predicted post-radiation thyroid dysfunction (AUC-ROC 0.84, CI95% 0.73–0.95, p < 0.001). V30 could serve as a dosimetric predictor of hypothyroidism following neck radiotherapy. This study underscores that a predictive model encompassing cancer type and site, along with V15, V30, VS15, VS30, can effectively anticipate post-radiation hypothyroidism. Fereshteh Talebi, (she/her/hers), MD (Presenting Author) - Weill Cornell Medicine, NY, USA; Ahmad Ameri (he/him/his), MD (First-Author) - Shahid Beheshti University of Medical Sciences , Tehran, Iran; Zohre Azma (she/her/hers), PhD (Co-Author) - Erfan Radiation Oncology Center, Tehran, Iran; Khashayar Fattah (he/him/his), MD (Co-Author) - University of Tennessee Medical Center Knoxville, TN, USA; Nazanin Rahnama (she/her/hers), MD (Co-Author) - Nikan Hospital, Tehran, Iran; Mansour Lesan (he/him/his), MD (Co-Author) - Shahid Beheshti University of Medical Sciences ; Sanaz Poshtmahi, PhD (Co-Author) - Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran; Farahnaz Rahimi, PhD (Co-Author) - Erfan Radiation Oncology Center, Tehran, Iran; Farzad Taghizadeh-Hesary (he/him/his), MD (Corresponding Author) - Clinical Oncology Department, Iran University of Medical Sciences, Tehran, Iran