The Clinical Value Of F-Fluorodeoxyglucose PET / CT And ¹⁸ F-Fluorothymidine PET / CT In The Diagnosis And Treatment Of Nasopharyngeal Carcinoma

Part One Predictive Value of18F-Fluorodeoxyglucose PET/CT for Long-term Survival of Patients with Nasopharyngeal CarcinomaBackground and Objective Parameters of F-Fluorodeoxyglucose (FDG) PET provide biological information of tumors. More and more studies have now focused on the prognostic value of FDG PET for nasopharyngeal carcinoma (NPC). But till now, most studies have only focused on one or two parameters, especially SUVmax, whose correlation with distant metastasis and survival has been disclosed preliminarily. The objective of this study was to fully utilize the metabolic information FDG PET provided, and to find the most valuable parameters for treatment outcome of nasopharyngeal carcinoma.Methods From June2007to December2010, NPC patients diagnosed and treated in our hospital and received FDG PET before treatment were retrospectively reviewed. All patients were treated with radical radiotherapy, with or without chemotherapy. Following PET parameters were recorded:SUVmax-T, SUVmean-T, MTV-T, TLG-T, SUVmax-N, Total SUVmax, Total SUVmean, Total MTV, Total TLG. The optimal cut-off values of above parameters were determined by receiver operating characteristic (ROC) analysis following the method of Metz. The primary endpoint was distant metastasis-free survival (DMFS), and the secondary endpoints were progression-free survival (PFS) and overall survival (OS). The predictive value of PET parameters for prognosis was analyzed.Results43consecutive patients were analyzed, and the median follow-up period was32months (range,23-68months). At the end of follow-up,4patients had died,4experienced local recurrence and2experienced nodal recurrence, and distant metastases happened in8patients, Distant metastasis is the main cause of treatment failure. The3-year DMFS, PFS and OS were81.0%,69.1%and83.2%, respectively. Univariate analysis showed patients with SUVmax-T>8.70, SUVmean-T>4.30, MTV-T>12.71, TLG-T>58.08, Total SUVmax>27.14, Total MTV>49.79, Total TLG>235.46or stage T3-4had significantly poorer DMFS (p=0.042, p=0.008, p=0.023, p=0.023, p=0.024, p=0.033, p=0.016, p=0.015). Those with SUVmean-T>4.30had significantly poorer PFS (p=0.027), and those with Total TLG>235.46showed a trend of better PFD. Those with SUVmean-T>4.30or MTV-T>12.71were observed to have a trend of better OS. Multivariate analysis showed Total SUVmax was the independent factor for DMFS (p=0.046). Although SUVmean-T was also showed to be the independently factor for PFS and OS (p=0.026, p=0.035), this should be interpreted with caution, as all the optimal cut-off values of PET parameters by ROC analysis were based on the best trade-off between sensitivity and specificity for DMFS, not for PFS or OS. Pearson correlation analysis showed mediate to strong correlationship between Total SUVmax and SUVmax-T, and between Total SUVmax and SUVmax-N(Pearson coefficient:0.579and0.876; p=0.000and p=0.000).Conclusions Preliminary results indicated that the sum of SUVmax of primary tumor and cervical lymph nodes was an independent predictive factor for distant metastasis in NPC patients treated with IMRT. This result need to be validated by further clinical trials with a larger sample, and may help in definition of patients of high risk for distant metastasis, who need more aggressive treatment. Part Two Preliminary Results of18F-Fluorothymidine PET/CT and18F-Fluorodeoxyglucose PET/CT in Diagnosing, Staging, and Monitoring and Predicting Response to Chemoradiotherapy in Nasopharyngeal CarcinomaBackground and Objective18F-FDG PET shows the metabolic activity of tumor tissue, while18F-FLT is a new kind of radioactive tracer and18F-FLT PET shows the proliferative activity of tumor. The objective of this study was to observe the value of F-FLT PET in diagnosing, staging, and monitoring and predicting response to treatment in NPC (nasopharyngeal carcinoma), and to compare it with that of18F-FDG PET, thus providing basis for personalized treatment of NPC.Methods NPC patients with pathology of WHO Ⅱ or Ⅲ, newly diagnosed in our hospital were prospectively enrolled into this study. All patients received2cycles of TPF neoadjuvant chemotherapy (NAC), followed by concurrent chemoradiotherapy (CCRT). The standard plan of radiotherapy was70.4Gy to the gross tumor volume (GTV) in T3-4disease and66Gy to the GTV in T1-2disease by2.2Gy per fraction. Each patient underwent a pretreatment18F-FLT PET/CT and18F-FDG PET/CT, a second18F-FLT PET/CT and18F-FDG PET/CT after NAC. Tumor regression was also evaluated at55Gy and three months after radiotherapy. The following parameters of PET/CT were recorded:SUVmax-T, SUVmean-T, MTV-T, PTV-T, TLG-T and TLT-T of primary tumor, SUVmax-N, MTV-N, PTV-N, TLG-N and TLT-N of metastatic lymph nodes, and sum of parameters of primary tumor and lymph nodes recorded as: Total SUVmax, Total SUVmean, Total MTV, Total PTV, Total TLG and Total TLT. The differences and correlation between above parameters, and value of them in monitoring and predicting clinical response were analyzed.Results Thirteen patients were enrolled. All patients were stage III-IVb except one with stage II patient.11patients had completed chemoradiotherapy, while another2did not. After2cycles of NAC, the response rate was100%, with1complete regression (CR) and12partial regression (PR). Among the11patients who had completed chemoradiotherapy, at55Gy of radiotherapy, CR rate was63.64%(7/11) and PR rate was36.36%(4/11). All5patients who had completed CCRT for3months reached CR. The sensitivities of FLT PET and FDG PET in detecting primary tumor were both100%. PTV-T and TLT-T of FLT PET had mediate to strong correlation with T stage (Rho:0.611, p=0.026; Rho:0.611, p=0.026). All parameters of FLT PET decreased significantly after2cycles of NAC. Spearman Rank correlation analysis showed that pretreatment PTV-N and post-chemotherapy parameters including SUVmax-N, PTV-N, TLT-N, Total SUVmax, Total PTV and Total TLT had strong negtively correlation with tumor response at55Gy of radiotherapy. The following parameters of pretreatment FLT PET were significantly lower than those of FDG PET: SUVmax-T, SUVmax-N, SUVmean-T and Total SUVmax (p=0.002, p=0.031, p=0.003, p=0.013). In addition to SUVmax-T, other parameters of FLT PET all showed moderate to strong correlation with those of FDG PET. The value of FLT PET in monitoring and predicting tumor response of NPC is comparable to FDG PET.Conclusions’8F-FLT PET, as a kind of new technique of functional imaging, is able to show proliferative status of primary lesions and metastatic lymph nodes of NPC. The value of FLT PET in diagnosing, staging, monitoring and predicting clinical response of NPC is comparable with18F-FDG PET, which still needs further research.