3464 - Dynamic Changes In Apparent Diffusion Coefficient Predict Radiation-Induced Sternocleidomastoid Muscle Atrophy In Nasopharyngeal Carcinoma
Presenter(s)
M. Fan1, W. Zhou2, Z. Chen3, M. Feng4, L. Li5, H. Wang6, and J. Lang1; 1Sichuan Cancer Hospital and Research Institute, University of Electronic Science and Technology of China, Chengdu, China, 2Sichuan cancer hospital, Chengdu, Sichuan, China, 3The Second Affiliated Hospital of Chongqing Medical University, Chongqing, Chongqing, China, 4The Third People's Hospital of Sichuan Province, Chengdu, China, 5Department of Radiation Oncology, Sichuan Cancer Hospital and Institute, Sichuan Cancer Center, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China, 6The Third People's Hospital of Sichuan Province, chengdu, China
Purpose/Objective(s): Predictive research on post-radiotherapy cervical muscle atrophy in head and neck cancer is limited. The absence of early quantitative tools delays intervention and impairs quality of life. This study uses functional MRI to evaluate dynamic ADC changes in the sternocleidomastoid muscle during chemoradiotherapy for nasopharyngeal carcinoma and assess their early predictive value for long-term muscle atrophy and radiation-induced soft tissue injury.
Materials/Methods:
This study was a secondary analysis of a phase II trial. Patients with stage II–IV nasopharyngeal carcinoma treated with definitive concurrent chemoradiotherapy were prospectively enrolled. MRI was performed at four time points: pre-radiotherapy (T0), at the 15th fraction of radiotherapy (T1), 3 months post-radiotherapy (T2), and >18 months post-radiotherapy (T3). Diffusion-weighted imaging and corresponding apparent diffusion coefficient maps were acquired at T0–T2. Regions of interest were delineated slice-by-slice for bilateral sternocleidomastoid muscles to extract mean ADC and muscle volume at each time point. The changes in mean ADC value (dADC%) and muscle volume reduction rate (dVOL%) were calculated. The mean dose delivered to the SCM was derived from the treatment planning system. Late radiation-induced soft tissue toxicity was assessed during long-term follow-up using the CTCAE, RTOG, and LENT-SOMA scales. Correlation and multivariable regression analyses were used to assess relationships among dose, ADC change, and muscle atrophy. Predictive performance was evaluated using receiver operating characteristic curve analysis.Results:
A total of 41 patients were included in the analysis. Compared with T0, SCM ADC increased at T1 and remained elevated at T2 (T1: dADC% = 19.999% ± 5.120%; T2: 16.414% ± 11.551%). Muscle volume loss was minimal at T1 (dVOL% = 0.782% ± 2.689%), became evident at T2 (12.559% ± 5.874%), and further progressed at T3 (24.653% ± 7.640%).Mean dose to the SCM showed a strong Spearman correlation with dADC% at T1 (? = 0.664, P = 2.26 × 10?6) and a moderate correlation at T2 (? = 0.401, P = 0.009). Both T1 and T2 dADC% were correlated with long-term volume loss (T1: ? = 0.438, p = 0.004; T2: ? = 0.444, p = 0.003). After adjustment, dADC% at T2 remained an independent predictor of long-term atrophy (ß = 0.241; 95% CI: 0.059–0.422; p = 0.011). Higher T1 dADC% was associated with increased risk of LENT-SOMA grade = mild toxicity (OR per 5% increment = 4.76; 95% CI: 1.35–16.73; p = 0.015). Both T1 and T2 dADC% showed moderate discrimination for pronounced atrophy (T3 dVOL% = 25%), with AUCs of 0.730 and 0.718, respectively.Conclusion: In NPC patients undergoing radiotherapy, SCM ADC elevation precedes volumetric muscle loss. dADC% at mid- (T1) and early post-radiotherapy (T2) is associated with long-term muscle atrophy and late toxicity, supporting ADC as an early imaging biomarker for radiation-induced cervical muscle injury and enabling risk stratification and follow-up management.