The value of posttreatment 18F-FDG PET/CT biomarkers for assessing response in metastatic nasopharyngeal carcinoma treated with PD-1 inhibitors.

PURPOSE: This study investigated the prognostic value of 18F-PET/CT parameters in patients with metastatic nasopharyngeal carcinoma (NPC) treated with gemcitabine-cisplatin (GP) and programmed cell death protein 1 (PD-1) inhibitors as first-line therapy.

METHODS

This retrospective study analyzed 219 patients who underwent baseline PET/CT including 61 with interim PET/CT post-3 treatment cycles. Metabolic indices included maximum standardized uptake value (SUVmax), SUVmean, SUVpeak, total lesion glycolysis (TLG), and total metabolic tumor volume (TMTV) were evaluated. Tumor responses assessed by different response criteria were compared. Prognostic thresholds for PET/CT parameters were determined by receiver operating characteristic (ROC) curves and survival analyses. The correlation between tumor responses and clinical outcomes was also assessed.

RESULTS

With a median follow-up of 36.37 months (IQR: 25.30-48.20), baseline metabolic parameters correlated with clinical stages, EBV DNA levels, and lactate dehydrogenase. Tumor response assessed using PET Response Criteria in Solid Tumors (PERCIST) showed superior prognostic value for overall survival (OS) (HR = 9.485, p < 0.001) and progression-free survival (PFS) (HR = 4.819, p < 0.001) compared to other criteria. At baseline PET/CT, TMTV1 and TLG1 were predictive of the survival outcomes. At interim PET/CT, all parameters were predictive for OS and PFS. The interim biomarkers were more valuable than the baseline parameters and the residual TLG2 was the most promising prognostic biomarker (area under the receiver operating characteristic curve [AUC] = 0.786 for OS; AUC = 0.731 for PFS).

CONCLUSION

Residual TLG2 post-3-cycle treatment emerged as a promising prognostic predictor in metastatic NPC patients receiving GP-ICI therapy. PERCIST-assessed tumor response reliably predicted early treatment outcomes.