Abstract 476: Clinical characteristics and outcome of pathologic N0 NSCLC patients with false positive on FDG PET-CT

Abstract

Background Preoperative Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (FDG PET-CT) is a non-invasive and useful diagnostic tool to evaluate mediastinal lymph node metastasis in lung cancer. However, there are often false-positive lymph node cases in FDG PET-CT. We enrolled patients diagnosed with clinical N1-3 on FDG PET-CT, but pathologic N0 after mediastinal lymph node dissection. We aimed to explore clinical characteristics and outcome of pathologic N0 non-small cell lung cancer patients with false positive mediastinal lymph nodes on FDG PET-CT. Methods We enrolled total 147 patients who took pre-operative PET-CT scan and mediastinal lymph node dissection. Among them, 40 patients were diagnosed with clinical N1-3 by PET-CT. These patients were re-evaluated by post-operative pathologic nodal metastasis and divided into false-positive group and others. We retrospectively analyzed clinicopathologic features and recurrence free survival among patients diagnosed with same pathologic stage. Results Among 40 patients diagnosed with clinical N1-3 on FDG PET-CT, 19 (47.5%) patients were pathologic N0, which means false positive lymph node by PET-CT. Preoperative absolute platelet count (279.79 x 109/L versus 218.67 x 109/L; P = 0.012) and Platelet-Lymphocyte Ratio (PLR, 16.93 versus 11.53; P = 0.012) were significantly higher in the patients with pathologic N0. Among patients with pathologic N0, the presence of lymphatic invasion was significantly lower than other group (31.6% versus 85.7%; P = 0.001). Recurrence free survival was significantly shorter in pathologic N0 patients than those with same pathologic stage (P = 0.037). In addition, cox regression analysis showed smoking status (P = 0.045) and lymphatic invasion (P = 0.047) were independent factors for recurrence, significantly. Conclusions In conclusion, higher absolute platelet count, PLR and lower proportion of lymphatic invasion were associated with false positive mediastinal lymph node on preoperative FDG PET-CT. Furthermore, recurrence free survival was significantly shorter in these patients than those with same pathologic stage. In the future, preoperative biomarkers to predict pathologic nodal status need to be investigated. Citation Format: Changdong Yeo, Hye Seon Kang, Sang Haak Lee. Clinical characteristics and outcome of pathologic N0 NSCLC patients with false positive on FDG PET-CT [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 476.