The Value Of ¹⁸F-FDG PET/CT In Staging And Delineation Of Target Volume In Nasopharyngeal Carcinoma

PART ONE: The Value of ¹⁸F-FDG PET/CT in Staging of Patients with Nasopharyngeal CarcinomaObjective: Nasopharyngeal carcinoma is one of common malignant tumors in our country. Radiation therapy is the main method of treatment at present. It’s important to determine the scope of the primary tumor accordingly. The aim of the study was to investigate the value of ¹⁸F-fluoro deoxidization glucose(¹⁸F-FDG) positron emission tomography/computed tomography（PET/CT）in staging of nasopharyngeal carcinoma（NPC）.Methods:Clinical data of 35 NPC patients who received treatment in the First Affiliated Hospital of Soochow University from Jan, 2010 to Feb, 2015 were studied retrospectively. 17 cases were pretherapeutic patients（14 males and 3 females, aged 14 to 68 years）. 13 cases of the pretherapeutic patients were certified poorly differentiated squamous cell carcinoma, 2 cases were non-keratinizing carcinoma, 1 case was vesicular nucleus cell carcinoma and 1 case was lymphoepithelial carcinoma. 18 cases were postherapeutic patients received radiotherapy and chemotherapy（13 males and 5 females, aged 21 to 73 years）. 12 cases of postherapeutic patients were certified poorly differentiated squamous cell carcinoma and 6 cases were non-keratinizing carcinoma. The patients were staged according to the results of ¹⁸F-FDG PET/CT, CT and MR. The correlations of whole body lesions SUVmax and nasopharynx SUVmax with T stage and clinical stage were analysized by the Spearman correlation analysis.Results:（1） The tumor sites of 17 pretherapeutic patients were all clearly displayed by PET/CT. The range of SUVmax was 3.29 to 13.0. Compared to CT/MR, PET/CT up-staged 6 patients（6/17） in the T stage, 1 patient（1/17） in the N stage and 1 patient（1/17） in the M stage. PET/CT down-staged 4 patients in the N stage.（2） PET/CT examination were positive in 11 cases, the range of SUVmax was 2.63 to 9.47. 7 cases were negative. The diagnostic sensitivity, specificity, PPV and NPV of ¹⁸F-FDG PET/CT and conventional imaging was 100%（9/9）, 55.6%（5/9）, 69.2%（9/13）, 100%（5/5） and 77.8%（7/9）, 44.9%（4/9）, 58.3%（7/12）, 66.7%（4/6）, respectively. 1 case was up-staged in the T stage, 2 cases in the N stage, 5 cases in the M stage. 1 case was down-staged in the N stage.（3） The correlation of whole body lesions SUVmax with T stage was 0.677（P<0.05）, with clinical staging was 0.667（P<0.05）. Nasopharynx SUVmax with T staging was 0.71（P<0.05）, with clinical staging was 0.46（P<0.05）.Conclusion: ¹⁸F-FDG PET/CT is more accurate than conventional imaging in the diagnosis of cervical lymph node and distant metastasis. The sensitivity, specificity, positive predictive value and negative predictive value of the diagnosis of recurrent nasopharyngeal carcinoma metastasis were higher than CT/MR. And this study have shown the positive correlation of whole body lesions SUVmax with T staging.PART TWO: The Value of ¹⁸F-FDG PET/CT in Delineation of Target Volume in Nasopharyngeal CarcinomaObjective: To compared the difference of ¹⁸F-FDG PET/CT and conventional imaging in outlining the target of nasopharyngeal carcinoma. To define a suitable threshold setting for gross tumor volume（GTV） by using PET/CT for radiotherapy planning in Nasopharyngeal carcinoma（NPC）.Methods:Clinical data of 14 pretherapeutic NPC patients who underwent ¹⁸F-FDG PET/CT examination in the First Affiliated Hospital of Soochow University from Jan, 2010 to Feb, 2015 were studied retrospectively. Tumor volume based on MRI/CT was defined as GTV.Biological target volumes（BTV） were derived from PET/CT based GTV of primary tumors. Various threshold method（20%, 30%, 40%, 50%, 60% SUVmax） and SUV fixed value（SUV values were 2.0, 2.5, 3.0, 3.5, 4.0） based on PET/CT were used to determine as BTV. The BTVs was defined as the volumes when BTV adjusted with GTV. To obtain the match rates between BTV and GTV in various SUV fixed value and threshold methods.Results:（1）: The BTV of 20% SUVmax group was 35.84±17.38cm3,30% SUVmax group was 14.94±8.25cm3,40% SUVmax group was 7.73±4.73cm3,50% SUe Vmax group was 4.41±3.09cm3 and 60% SUVmax group was 2.37±2.03cm3. There was no significant difference between 30% SUVmax group and 40% SUVmax group, 40% SUVmax group and 50% SUVmax group. There were significant difference among the other groups, F=29.62, P < 0.05. The BTV of SUV2.0 group was 63.99±25.5cm3, SUV2.5 group was 34.29±18.02cm3,SUV 3.0 group was 23.78±10.95 cm3,SUV3.5 group was 14.78±7.27 cm3 and SUV 4.0 group was 9.93±5.82 cm3. There was no significant difference between SUV3.0 group and SUV3.5 group, SUV3.5 group and SUV 4.0 group. There were significant difference among the other groups, F=25.37,P<0.05.（2）: The matching rate between the BTV of SUV2.5 group and GTV was（60.63±40.95）%（3）: The matching rates between different threshold methods outlined BTV and GTV were（50.77 ± 30.86）%,（88.14 ± 59.81）%,（42.78 ± 20.12）%,（24.22 ± 12.38）% and（12.45 ± 7.51） %. And the matching rates between SUV fixed value method outlined BTV and GTV was（404.85 ± 223.22）%,（221.65 ± 134.84）%,（143.96 ± 73.45）%,（88.48 ± 43.43）% and（59.24 ± 31.8）%, respectively.（4）: The GTV of 14 cases of nasopharyngeal carcinoma was 19.64±9.74 cm3. s TL（%） was（27.15±5.32）% and s SUV was 3.18±0.63.Conclusion: The matching rate between the BTV accordingly based SUVmax 2.5 and GTV was moderate. The matching rate between the BTV based on the threshold method 30%SUVmax or fixed SUV3.5 value and GTV was smaller.