Adding Maximum Standard Uptake Value of Primary Lesion and Lymph Nodes in 18F-Fluorodeoxyglucose PET Helps Predict Distant Metastasis in Patients with Nasopharyngeal Carcinoma

OBJECTIVE To find out the most valuable parameter of 18F-Fluorodeoxyglucose positron emission tomography for predicting distant metastasis in nasopharyngeal carcinoma. METHODS From June 2007 through December 2010, 43 non-metastatic NPC patients who underwent 18F-Fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) before radical Intensity-Modulated Radiation Therapy were enrolled and reviewed retrospectively. PET parameters including maximum standardized uptake value (SUV max), mean standardized uptake value (SUV mean), metabolic tumor volume (MTV), and total lesion glucose (TLG) of both primary tumor and cervical lymph nodes were calculated. Total SUV max were recorded as the sum of SUV max of primary tumor and cervical lymph nodes. Total SUV mean, Total MTV and Total TLG were calculated in the same way as Total SUV max. RESULTS The median follow-up was 32 months (range, 23-68 months). Distant metastasis was the main pattern of treatment failure. Univariate analysis showed higher SUV max, SUV mean, MTV, and TLG of primary tumor, Total SUV max, Total MTV, Total TLG, and stage T3-4 were factors predicting for significantly poorer distant metastasis-free survival (p = 0.042, p = 0.008, p = 0.023, p = 0.023, p = 0.024, p = 0.033, p = 0.016, p = 0.015). In multivariate analysis, Total SUV max was the independent predictive factor for distant metastasis (p = 0.046). Spearman Rank correlation analysis showed mediate to strong correlationship between Total SUV max and SUV max-T, and between Total SUV max and SUV max-N(Spearman coefficient: 0.568 and 0.834; p = 0.000 and p = 0.000). CONCLUSIONS Preliminary results indicated that Total SUV max was an independently predictive factor for distant metastasis in patients of nasopharyngeal carcinoma treated with Intensity-Modulated Radiation Therapy.