Abstract
<title>Abstract</title> <p> Background Immunotherapy is ineffective in recurrent or metastatic nasopharyngeal carcinoma (RM-NPC) refractory to standard chemotherapy. Therefore, new biomarkers must be considered for identifying patients with RM-NPC who may benefit from immunotherapy. To investigate the role of intravoxel incoherent motion diffusion-weighted MR imaging (IVIM-DWI) for noninvasively assessing tumor-infiltrating lymphocytes (TILs) and immunotherapy prognosis in RM-NPC refractory to standard chemotherapy. Methods 67 patients with RM-NPC refractory to standard chemotherapy were retrospectively identified. All patients underwent nasopharyngeal IVIM-DWI scans prior to immunotherapy. IVIM parameters, including the apparent diffusion coefficient (ADC), pure diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction ( <italic>f</italic> ), were measured. Four TIL biomarkers (CD4, CD8, FOXP3, and CD20) were detected, and the histochemistry score (H-score) was calculated. A TIL-based immunoscore signature was also developed. Results The median follow-up period was 17 months. Among the 67 patients, 36 (53.73%) had died. The immunoscore was positively correlated with the overall survival (OS) (P < 0.001). Kaplan–Meier analysis indicated that the high-immunoscore group had significantly longer OS than that of the low-immunoscore group (P < 0.001). The ADC (P = 0.016) and D (P = 0.003) values were negatively correlated with the immunoscore, while the f value (P = 0.011) was positively correlated with it. Conversely, higher ADC (≥ 0.74 × 10 − 3 mm2/s) and higher D (≥ 0.50 × 10 − 3 mm2/s) were negatively associated with OS, while higher f (≥ 0.33) was positively associated with it (all P < 0.05). Conclusion IVIM parameters could noninvasively evaluate TIL infiltration and predict immunotherapy prognosis in RM-NPC. </p>