The prognostic value of intra- and peritumoral habitat analysis in nasopharyngeal carcinoma: combining IVIM and ASL.

objectivesTo evaluate the value of intravoxel incoherent motion (IVIM) and arterial spin labeling (ASL)-based habitat analysis of intra- and peritumoral regions for predicting overall survival (OS) and progression-free survival (PFS) in NPC. MATERIALS AND

methods106 patients were prospectively included. Primary tumors were delineated on T2-weighted imaging, and three peritumoral regions (3, 5, and 10 mm) were automatically dilated and manually corrected according to the clinical tumor volume outlining criteria. The pure diffusion coefficient (D) and mean kurtosis (MK) maps of IVIM, and blood flow (BF) map of ASL were used for habitat analysis. Volume fraction and histogram parameters (Mean, Kurtosis and Skewness) were extracted for each subregion. Univariate and multivariate Cox analyses were used to construct intra- and peritumoral, Clinic, and combined models, which were assessed by the C-index. Nomogram, calibration curves, and Kaplan-Meier curves were also plotted.

resultsThe intratumoral subregion 4 was characterized by high D and low BF and MK value, representing the radiotherapy-resistant region, and patients with treatment failure had a higher proportion of subregion 4. The Intra-score independently predicted OS (hazard ratio (HR): 1.023, p = 0.002) and PFS (HR: 1.028, p = 0.001). Combined clinical factors with intra- and peritumoral habitat features showed the highest performance (C-index: 0.780 [OS] and 0.721 [PFS]) and outperformed the Clinic model (C-index: 0.691 [OS] and 0.666 [PFS], p ≤ 0.03). The post hoc subgroup analysis confirmed robustness.

conclusionPeri-tumoral regions provide valuable prognostic information. Combining IVIM-ASL-based habitat analysis offers a noninvasive approach to predicting treatment outcomes. KEY POINTS: Question The prognostic value of the peritumoral region in nasopharyngeal carcinoma remains unclear, with limited identification of treatment-resistant subregions. Findings The intratumoral subregion 4 may represent the radiotherapy-resistant region, and combining the intratumoral region with 3-mm peritumoral regions improved prognostic prediction performance. Clinical relevance Arterial spin labeling and intravoxel incoherent motion-based habitat analysis can define radiotherapy-resistant subregions, and the peritumoral region contains valuable prognostic information that should not be disregarded.