Quantitative MRI in the assessment of clival invasion in locally advanced nasopharyngeal carcinoma.

OBJECTIVE: This study assesses the value of quantitative magnetic resonance imaging (qMRI) in evaluating clival invasion (CI) and monitoring therapeutic response in locally advanced nasopharyngeal carcinoma (LA-NPC). It also investigates the relationship between qMRI parameter changes in CI and regression of nasopharyngeal soft-tissue invasion. METHODS: In this prospective study, fifty-five LA-NPC patients with CI from a single-center underwent qMRI at baseline (t0), pre-radiotherapy (t1), mid-radiotherapy (t2), and post-radiotherapy (t3). T1, T2, and T2* mappings were measured in manually delineated volumes of interest. Patients were categorized into complete response (CR) and non-CR groups based on nasopharyngeal soft tissue tumor regression per RECIST 1.1. The cervical vertebrae served as self-controls. RESULTS: At baseline, T1, T2, and T2* mapping values were significantly higher in clival invasion than in normal cervical vertebrae (p < 0.001). During treatment, the CR group (87.3%) exhibited marked decreases in T1 values (from 841.30 [IQR:521.31] ms at baseline to 587.61 [IQR: 187.54] ms at post-RT; p<0.001) and T2* values (from 7.27 [IQR: 5.28] ms to 4.86 [IQR: 3.48] ms; p<0.001), accompanied by a significant increase in T2 values (from 89.83 [IQR: 18.25] ms to 99.79 [IQR: 12.10] ms; p<0.001), whereas the non-CR group showed no significant alterations in T1 and T2 mapping values (p > 0.05). Notably, there were no significant differences in T1, T2, and T2* mapping values between t2 and t3 in the CR group (p > 0.05). Furthermore, differences between CI and cervical vertebrae measurements (ΔT1, ΔT2, ΔT2*) diminished in the CR group during treatment (p < 0.05). Conversely, the non-CR group showed no significant changes in ΔT1 (p = 0.738) mapping values but did exhibit changes in ΔT2 and ΔT2* mapping values (p < 0.001). CONCLUSIONS: The qMRI-derived T1, T2, and T2* mapping demonstrates potential utility in monitoring CI response in LA-NPC, serving as an inherently quantitative tool that warrants further investigation in larger cohorts.