Value of spectral CT in differentiating post-treatment recurrence/residual tumor from inflammatory fibrosis in nasopharyngeal carcinoma

This prospective, single-center pilot study aims to investigate the potential value of spectral computed tomography (CT) in differentiating post-treatment recurrence/residual tumor from inflammatory fibrosis in patients with Nasopharyngeal Carcinoma (NPC). This prospective study included 44 patients with previously treated NPC who underwent spectral CT either for suspected recurrence or for routine follow-up. Based on pathological results, 16 patients were diagnosed with recurrence/residual tumor and 21 with inflammatory fibrosis, while 7 were classified as normal based on follow-up findings. Quantitative parameters were measured in arterial phase (AP), venous phase (VP), and late delayed phase (LDP). The analyzed parameters included conventional image (CI) CT values, iodine concentration (IC), normalized iodine concentration (NIC), virtual mono-energetic imaging (VMI) with CT values at 40 keV and 100 keV, spectral curve slope (λ HU), extracellular volume (ECV) fraction, arterial enhancement fraction (AEF), and normalizing arterial enhancement fraction (NAEF). Group comparisons were performed with ANOVA or Kruskal–Wallis tests, with post hoc LSD analysis. Diagnostic performance was assessed with ROC analysis. AEF AP/LDP , and NAEF AP/LDP perform well in distinguishing between NPC recurrence/ residual tumor and inflammatory fibrosis ( P < 0.05). AEF AP/LDP and NAEF AP/LDP demonstrated the highest performance ( P < 0.001). Their optimal cutoff values were 0.63 and 0.11, with corresponding AUCs of 0.887 (95% CI: 0.673–0.964) and 0.789 (95% CI: 0.548–0.879), sensitivities of 93.8% and 75.0%, and specificities of 71.4% and 76.2%, respectively. Furthermore, a combined model incorporating the six significant spectral CT parameters achieved a higher apparent AUC of 0.914 (95% CI: 0.840–1.000), with a sensitivity of 93.8% and a specificity of 81.0%. In this prospective single‑center pilot study, spectral CT–derived quantitative parameters, particularly AEF AP/LDP and NAEF AP/LDP , showed promising preliminary discriminatory potential for distinguishing post‑treatment recurrence/residual lesions from inflammatory fibrosis in patients with nasopharyngeal carcinoma.