¹⁸F-FDG uptake by primary tumor as a predictor of intratumoral lymphatic vessel invasion and lymph node involvement in non-small cell lung cancer: Analysis of a multicenter study

Intratumoral lymphatic vessel invasion and lymph node involvement are important factors in the planning of therapeutic strategies, particularly limited surgical resection in patients with non-small cell lung cancer. ¹⁸F-FDG uptake within the primary lesion correlates with aggressiveness on PET studies. The more metabolically active the tumor, the more aggressive are the findings. The aim of this multicenter study was to determine whether ¹⁸F-FDG uptake of the primary tumor is a predictor of intratumoral lymphatic vessel invasion and lymph node metastasis in patients with non-small cell lung cancer. Methods: One hundred thirty-two patients with lung cancer were studied. All patients underwent a thoracotomy within 4 wk of the ¹⁸F-FDG PET study. A 3-point visual scoring system (low, moderate, or high grade in comparison with mediastinal activity) was used to interpret ¹⁸F-FDG uptake within the primary lesions. The degree of ¹⁸F-FDG uptake in the primary tumor was correlated with the incidence of intratumoral lymphatic vessel invasion and lymph node involvement. Multivariate analysis was performed with logistic multivariate analysis to assess the joint effects and interactions of the variables (age, sex, tumor size, histology, and ¹⁸F-FDG uptake) on intratumoral lymphatic vessel invasion and lymph node involvement. Results: Intratumoral lymphatic vessel invasion and lymph node involvement were found in 7.1% and 5.9%, respectively, of the patients classified in the low-grade group, and in 14.3% and 10.0%, respectively, of the patients classified in the moderate-grade group. In contrast, of the patients classified in the group with high ¹⁸F-FDG uptake, intratumoral lymphatic vessel invasion and lymph node involvement were found in 39.7% and 38.9%, respectively. Multivariate analysis showed that only ¹⁸F-FDG uptake was a significant factor for intratumoral lymphatic vessel invasion and that tumor size and ¹⁸F-FDG uptake were significant factors for lymph node involvement. Of the patients in the high-grade group whose tumors were classified as ≥3 cm in size, lymph node involvement was found in 51.5%. In contrast, of the patients in the low-to moderate-grade group whose tumors were classified as <3 cm in size, lymph node involvement was found in only 9.1% (P < 0.0001). Conclusion: Patients with a low to moderate ¹⁸F-FDG uptake in the primary lesion had a significantly lower risk of concurrent intratumoral lymphatic vessel invasion and nodal involvement than did patients with a high ¹⁸F-FDG uptake. In patients with non-small cell lung cancer, ¹⁸F-FDG uptake by the primary tumor is a strong predictor of intratumoral lymphatic vessel invasion and lymph node metastasis.