Purpose: This article evaluates [18F] fluorodeoxyglucose positron emission tomography (18F-FDG-PET) findings as a predictor for local responders (R) vs. nonresponders (NR) in nasopharyngeal carcinoma (NPC) patients with Stage T4 lesions, before and at 3 months after completion of concurrent chemotherapy and radiation therapy (CCRT).
Methods and materials: From January 2002 to November 2003, 39 T4 NPC patients were enrolled. All had magnetic resonance imaging and 18F-FDG-PET, both before and 3 months after CCRT. Any residual/recurrent lesions were confirmed histopathologically.
Results: Of the 39 eligible patients, after a follow-up of 24.2 +/- 9.5 months, 35 became disease-free and 4 had residual or recurrent disease. Marginal differences in standard uptake values (SUV) were observed (10.9 +/- 5.3 vs. 15.6 +/- 3.4, p = 0.058) between R and NR before treatment, and value changes of SUV before and after CCRT were not significantly different. However, highly significantly lower values of SUV were noted for R than for NR 3 months after completion of CCRT (2.1 +/- 0.8 vs. 5.5 +/- 3.2, p = 0.001). One hundred percent positive and negative predictive values were observed for SUV values of 4.0, set 3 months after completion of CCRT.
Conclusions: Neither the pretreatment SUV nor the changes of SUV between pretreatment and posttreatment were significant predictors for local response. SUV at 3 months after completion of CCRT was a significant determinator for local response. The cutoff of 4.0 for SUV at 3 months after completion of CCRT was useful to be offered as a diagnostic reference for recurrent or residual tumor for NPC treatment.