| [Purpose] The aim of this study was to investigate the diagnostic and prognostic value of whole body 18F-fluorodeoxy glucose positron emission tomography/computed tomography (18F-FDG PET/CT) imaging in patients referred with cervical nodal metastatic carcinoma of unknown primary site (CCUP).[Methods] A total of 137 consecutive patients [95 males,42 females, age range 24-84 (55.77+11.71) years old] with histological proven CCUP who underwent PET/CT imaging to find primary tumors between March 2010 and June 2015 in our PET/CT center were retrospectively analyzed. The golden standard was the final clinical pathological diagnosis or long-term follow-up (> 6 months) results. The diagnostic sensitivity, specificity and accuracy of 18F-FDG PET/CT imaging in detecting primary tumors were calculated, also the positive predictive value and negative predictive value. Chi-square test was conducted to identify if there was any difference between any prognostic factors (including sex, age, histopathologic tumor type, side of lymph node involvement, lymph node level, presence or absence of distant metastasis and SUVmax of cervical node) in the primary found or not by PET/CT imaging. Kaplan-Meier analysis was conducted for survival analysis and to identify the presence of any prognostic factors (including age,sex, presence or absence of distant metastasis, lymph node level, side of lymph node involvement, histopathologic tumor type and primary found or not by PET/CT imaging). ANOVA was used to detect whether there was statistically significant differences in the SUVmax of involved cervical lymph nod between the death and survivors. ROC curve was used to determine the optimal diagnostic cutoff of the SUVmax of cervical lymph node. P< 0.05 was considered statistically significant.[Results] Whole body 18F-FDG PET/CT scan correctly detected the primary tumor in 63.5%(87/137) of patients with histologically proven CCUP. The diagnostic sensitivity, specificity, accuracy, positive predictive value and negative predictive value were 90.6% (87/96),80.5%(33/41),87.6%(120/137),91.6%(87/95) and 78.6%(33/42) respectively. The head-neck and lung areas were the two most commonly detected primary tumor sites [34.3%(47/137),23.4%(32/137) respectively]. Furthermore, in 40.1%(55/137) patients, 18F-FDG PET/CT detected extra-nodal distant metastases (M stage) leading to a re-staging and possibly influencing subsequent treatment plans.Even though by the end date of the study,59.1%(81/137) of patients were still alive, survival analysis was carried out. Discoveries of distant metastasis and inferior cervical lymph nodes metastasis were associated with the worst survival (x2=20.990,12.277, both P<0.01). One-way ANOVA analysis showed a striking difference in lesions glucose metabolism between the decedent and survivals, with SUVmax 10.94±5.76,8.58±5.03 respectively (F=5.829, P<0.05). The ROC curve revealed patients with SUVmax>6.5 were of higher mortality risk than those with SUVmax<6.5 (?2=7.120, P<0.01). There were no statistically significant associations between other factors and prognosis.[Conclusions] The present study indicates Whole-body 18F-FDG PET/CT scan is a significant and valuable tool in the identification of the primary tumor site in patients with CCUP. Furthermore,18F-FDG PET/CT scan are of value in the assessment of prognostic analysis without the need of identification of the primary tumors. |
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