Assessment of tumor response to definitive chemoradiotherapy and prognosis prediction in patients with esophageal cancer judged by PET response criteria in solid tumors: multicenter study in Japan.

OBJECTIVES: The aim of the study was to evaluate PET response criteria in solid tumors (PERCIST) to indicate therapeutic response to definitive chemoradiotherapy, as well as prediction of recurrence and death in patients with esophageal cancer. METHODS: Before and after recieving definitive chemoradiotherapy, 181 patients with esophageal cancer underwent fluorodeoxyglucose-PET/computed tomography (FDG-PET/CT). PERCIST, reduction rates of tumor uptake and volume of whole lesions, tumor node metastasis (TNM) staging regarding progression-free survival (PFS), and overall survival (OS) were analyzed using log-rank and Cox methods. RESULTS: Complete metabolic response (CMR), partial metabolic response (PMR), stable metabolic disease (SMD), and progressive metabolic disease (PMD) shown by PERCIST were seen in 42 (23.2%), 113 (62.4%), 14 (7.7%), and 12 (6.6%) patients, respectively. Progression developed in 137 (75.7%) patients and 101 (56.1%) patients died (median follow-up 16.9, range 3.2-124.9 months). Those who achieved CMR showed significantly longer PFS and OS as compared with patients who did not (PMR, SMD, and PMD) (both P < 0.0001). In univariate analysis, initial clinical T status (P = 0.0048), N status (P = 0.011), and TNM stage (P = 0.0006), PERCIST (P < 0.0001), and reduction rate of peak lean body mass standardized uptake value (P < 0.0001), of metabolic tumor volume (P < 0.0001), and of total lesion glycolysis (TLG) (P < 0.0001) were associated with significantly increased OS. Multivariate analysis confirmed PERCIST [hazard ratio (HR): 13.15, 95% confidence interval (CI), 4.54-55.8; P < 0.0001], and TLG reduction rate (HR: 2.21, 95% CI, 1.04-4.68; P = 0.040) as independent OS predictors. CONCLUSION: PERCIST is useful for evaluating therapeutic response to definitive chemoradiotherapy, and predicting progression and death in patients with esophageal cancer.

Assessment of Mediastinal Tumors Using SUVmax and Volumetric Parameters on FDG-PET/CT.

OBJECTIVES: This study aimed to evaluate the role of pretreatment SUVmax and volumetric FDG positron emission tomography (PET) parameters in the differentiation between benign and malignant mediastinal tumors. In addition, we investigated whether pretreatment SUVmax and volumetric FDG-PET parameters could distinguish thymomas from thymic carcinomas, and low-risk from high-risk thymomas. METHODS: This study was conducted on 52 patients with mediastinal tumors undergoing FDG-PET/CT. Histological examination indicated that 29 mediastinal tumors were benign, and 23 cases were malignant. To obtain quantitative PET/CT parameters, we determined the maximum standardized uptake value (SUVmax), volumetric parameters, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) for primary tumors using SUVmax cut-off value of 2.5. SUVmax, MTV and TLG of benign and malignant tumors were compared using the Mann-Whitney U test. Moreover, receiver-operating curve (ROC) analysis was applied to identify the cut-off values of SUVmax, MTV and TLG for the accurate differentiation of benign and malignant tumors. SUVmax, MTV and TLG were compared between thymomas and thymic carcinomas, as well as low-risk and high-risk thymomas. RESULTS: Mean SUVmax, MTV and TLG of malignant mediastinal tumors were significantly higher compared to benign tumors (P<0.001). Sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of SUVmax were 78.2%, 86.2%, 82.6%, 81.8%, and 83.3%, respectively. These values were estimated at 82.6%, 96.6%, 90.4%, 95%, and 87.5% for MTV and TLG, respectively. Additionally, optimal cut-off values for the differentiation of benign and malignant mediastinal tumors were determined at 4.2 and 22.3 mL and 79.7 g for SUVmax, MTV and TLG, respectively. Mean SUVmax, MTV and TLG of thymic carcinomas were significantly higher compared to thymomas (P<0.01), while no significant differences were observed in the mean quantitative parameters between low-risk and high-risk thymomas. CONCLUSION: Although SUVmax, MTV and TLG could not distinguish between low-risk and high-risk thymomas, these parameters might be able to differentiate benign tumors from malignant mediastinal tumors noninvasively. These parameters could be used to distinguish between thymomas and thymic carcinomas as well. Therefore, FDG-PET/CT parameters seem to be accurate indices for the detection of malignant mediastinal tumors.