Staging in nasopharynx cancers f-18 prognostic value of volumetric parameters in F-18 FDG PET/CT imaging

Aim: Although nasopharyngeal carcinoma (NFC) is a non-endemic region for our country, the persistent state of the tumor, even in the early stages, has a high probability of recurrence and metastasis, and the prognosis may be poor. Although the personalized treatment protocol increases the disease survival, there is no method yet to determine which patient will be applied more aggressive treatment modalities. With this study, we aimed to determine the success of the volumetric parameters of staging F-18 Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in predicting the prognosis of the disease. Material and Methods: In this retrospective study, histopathological diagnosis of nasopharyngeal carcinoma was performed at Necmettin Erbakan University Meram Faculty of Medicine, Department of Nuclear Medicine between May 2010 and July 2021 for pre- treatment staging with FDG PET/CT imaging, then by the Radiation Oncology Department. A total of 62 patients who underwent definitive treatment were included. The patient files were reviewed retrospectively and the findings of gender, age, smoking-alcohol use, tumor stage, nodal stage, general stage of the disease, histopathological subtype, locoregional recurrence, distant metastasis, and survival were recorded. SUVmax, SUVmean, MTV and TLG values measured from the primary lesion and lymph node in the staging FDG PET/CT imaging, and NTR ratio were recorded. The value of these parameters in predicting disease recurrence, metastasis status and survival was investigated. Results: 62 patients were included in the study. The mean age of the patients was 49.6 ± 14.1 years. Fifty (80.6%) of the patients were male and 28 (45.2%) were smokers. There was 1 (1.6%) patient who used alcohol. According to tumor grade, 12 patients (19.4%) were reported as keratinized, 9 patients (14.5%) as differentiated non-keratinized, and 41 patients (66.1%) as undifferentiated non-keratinized. Eighteen (29%) of the patients were at T1 stage, 27 (43.5%) at T2 stage, 6 (9.7%) at T3 stage, and 11 (17.7%) at T4 stage. According to N staging, 9 (14.5%) patients were classified as N0, 9 (14.5%) patients as N1, 32 (51.6%) patients as N2, 10 (16.1%) patients as N3a and 2 (3.2%) patients as N3b. In general, 8 according to tumor size and lymph node involvement, 3 (4.8%) of the patients were stage 1, 11 (17.7%) stage 2, 28 (45.2%) stage 3 and 20 (32.3%) stage. It was classified as 4A. Considering the volumetric FDG PET/CT parameters, LN SUVmax, LN SUVmean values were found to be significantly higher in patients with distant metastases at follow-up (p<0.05 for each). NTR values were significantly lower in patients without distant metastases during follow-up (p=0.022). In the analysis of overall survival, locoregional recurrence-free and distant metastasis-free survival, no significant correlation was found with PET/CT volumetric parameters. Conclusion: In our thesis study, which was planned and conducted to investigate whether pre-treatment staging FDG PET/CT volumetric parameters have prognostic value in newly diagnosed NFC patients, a significant relationship between measured volumetric parameters and survival could not be established. On the other hand, SUVmax, SUVmean and new NTR values measured from metastatic lymph node were found to be significantly correlated in predicting distant metastasis. The use of these parameters together with anatomical staging, integrated risk assessment in terms of prognosis, and treatment classification of patients with poor prognosis will be guiding.