Abstract 142P
Background
Lung invasive mucinous adenocarcinoma (LIMA) is a rare and heterogeneous subtype of lung cancer, with patterns of lymph node metastasis unknown and consensus on LND strategy unreached. This study aimed to evaluate lymph node metastasis patterns in LIMAs and establish optimal lymph node dissection (LND) strategies.
Methods
Data from 19,596 lymph nodes from 1,474 LIMA patients were analysed. Metastasis probabilities were calculated for each lymph node station to construct a metastasis atlas. Statistical methods, including LOWESS fitting, restricted cubic spline, Kaplan-Meier, and Cox regression analyses, were employed to identify optimal LND strategies.
Results
Compared with nonmucinous adenocarcinoma patients, LIMAs had larger tumor sizes and a significant increase in the number of dissected lymph nodes. However, the probability of lymph node metastasis in patients with LIMA was significantly lower than that in nonmucinous adenocarcinoma (4.20% vs. 7.19%, p < 0.05), suggesting distinct patterns of lymph node metastasis. Metastasis was most common in the peripheral and upper zones (stations 3P and 14), with minimal involvement in the lower zone (stations 8 and 9). This pattern was also confirmed in 208 patients with N1/2 stage. A predictive model (AUC=0.837) identified a high-risk group with a significantly greater proportion of patients with stage N1+ disease (68.09% vs. 11.63%, p < 0.001) and aworse prognosis (HR=4.02, 95% CI:2.74–5.90, p < 0.001). Dissecting over 18 lymph nodes did not further improve the accuracy of N staging. A U-shaped relationship between the lymph node count and prognosis was found, with 6–25 lymph nodes as the optimal range. Excessive or insufficient dissection was closely related to poorer outcomes.
Conclusions
This study is the first to systematically reveal the LIMAspecific lymph node metastasis pattern and recommend LND strategies. We recommend using 18 lymph nodes as the optimal cut-off point for N staging, while dissection of 6 to 25 lymph nodes is crucial for tumor control and long-term prognosis. Appropriate adjustments can be made based on the metastasis atlas and predictive model in actual clinical practice.
Legal entity responsible for the study
The authors.
Funding
This work was supported by the National Key R&D Program of China (2022YFC2407404); Beijing Natural Science Foundation (7232134); CAMS Initiative for Innovative Medicine (2021-1-I2M-012); National High-Level Hospital Clinical Research Funding (2022-PUMCH-C-043); Beijing Hope Run Special Fund of Cancer Foundation of China (LC2021L01, LC2021B12); Beijing Municipal Science & Technology Commission (Z211100002921058); Administrative Research Fund, CHCAMS (LC2021D01).
Disclosure
All authors have declared no conflicts of interest.