The relationship between volumetric data obtained from F-18 FDG PET/CT and pathological findings in patients diagnosed with non-small cell lung cancer

Aim: This study aims to assess the association between metabolic parameters derived from F-18 FDG PET/CT, including SUVmax, SUVmean, TLG, and MTV, with histopathological subtypes and lymph node metastasis, as well as tumor localization in patients with non-small cell lung cancer (NSCLC). Matherials and Methods: A total of 249 patients diagnosed with primary NSCLC and who underwent PET/CT imaging for staging purposes were included in the study. Patients were classified according to histopathological subtypes (adenocarcinoma and squamous cell carcinoma), the presence of lymph node metastasis, and tumor localization. Differences in the non-normally distributed metabolic parameters, such as SUVmax, SUVmean, TLG, and MTV, between groups were assessed using the MannWhitney U test, and the predictive power of SUVmax for lymph node metastasis was evaluated using ROC analysis. Results: The findings demonstrated that patients with squamous cell carcinoma had significantly higher SUVmax, SUVmean, TLG, and MTV values compared to those with adenocarcinoma (p<0.001). In patients with lymph node metastasis, the median values of SUVmax, SUVmean, TLG, and MTV were statistically significantly higher than in those without metastasis (p<0.05). ROC analysis conducted to assess the ability of SUVmax to differentiate metastatic lymph nodes revealed an optimal cutoff value of 8.85 g/ml, with a sensitivity of 88.4% and a specificity of 30.6%. Evaluation based on tumor localization within the lung revealed no statistically significant differences in primary tumor SUVmax, SUVmean, TLG, or MTV values between centrally and peripherally located tumors. However, metastatic lymph nodes associated with peripheral tumors demonstrated significantly higher SUVmax LN and SUVmean LN values (p < 0.05). One of the limitations of our study is the potential difficulty in clearly delineating the borders of the lymph nodes with the highest SUVmax in centrally located tumors, as these often present with a conglomerate appearance involving adjacent lymphatic structures. In genderbased analyses, no significant differences were found between male and female patients regarding SUVmax, SUVmean, TLG, and MTV. However, TLG LN values measured in metastatic lymph nodes were significantly higher in male patients (p=0.01). Conclusion: Metabolic parameters obtained from F-18 FDG PET/CT may serve as strong predictors in identifying the biological differences among NSCLC subtypes and the presence of lymph node metastasis. Notably, SUVmax was determined to be a significant marker for detecting lymph node metastasis. Additionally, the observation that centrally located tumors exhibit higher metabolic activity suggests that these tumors may have a more aggressive clinical course. However, due to the low specificity of SUVmax, it should be considered alongside other clinical and histopathological parameters.