Selective Lymph Node Resection for Invasive Non-small Cell Lung Cancer With the CTR of 0.5-1 and the Diameter of ≤ 2 cm: a Prospective， Single-arm, Multi-center, Phase Ⅱ Trial

Selective lymph node dissection is an important idea to reduce the trauma of mediastinal lymph node dissection in early clinical patients. In a previous study, our team proposed a predictive model for mediastinal lymph node metastasis in patients with clinical T1N0 non-small cell lung cancer, and found that age, tumor size, central type, and pathologic subtype were closely related to mediastinal lymph node metastasis. In addition, our team found that adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), and invasive adenocarcinoma with predominantly adherent subtype (LPA) did not have mediastinal lymph node metastasis, and lymph node dissection was not necessary for such patients. In addition, by retrospectively studying nearly 3,000 cases of stage I-III NSCLC, we found that NSCLCs in the apical segments do not metastasize to the lower mediastinum, whereas in N1 lymph node-negative patients with negative pleural invasion, tumors in segments of the upper lobes do not metastasize to the lower mediastinal lymph nodes. On this basis, we conducted the first international prospective phase II clinical trial of a selective lymph node dissection strategy to validate the clinical feasibility of a selective lymph node dissection strategy. The main objective of this study was to develop a selective lymph node dissection strategy for cT1NOM0 invasive NSCLC with a diameter of ≤2 cm, i.e., no lower mediastinal lymph node dissection for tumors located in the upper lobe, and no upper mediastinal lymph node dissection for tumors located in the lower lobe. Further, we retrospectively analyzed 7067 NSCLC cases with systematic lymph node dissection from April 2008 to July 2022, in which the rate of mediastinal lymph node metastasis was 15.4% (1091/7067), and there was no lymph node metastasis in 209 cases of AIS/MIA/LPA, whereas in other subtypes of adenocarcinomas, the rate of mediastinal lymph node metastasis was 15.3% (106 /695). Among them, we retrospectively analyzed 360 cases of cT1N0M0 non-small cell lung cancer with 0.5 < CTR < 1.0 and found that among them, tumors located in the upper lobe had no lower mediastinal lymph node metastasis, and tumors located in the lower lobe had no metastasis in the upper mediastinal lymph nodes. For other non-small cell lung cancers with 0.5 < CTR < 1.0, if the VPI was negative, no lower mediastinal metastasis was also observed in tumors in the upper lobe and no upper mediastinal metastasis was observed in tumors in the lower lobe. In 212 cases of lung cancer not exceeding 1 cm in size, there were no lower mediastinal metastases in tumors in the upper lobe and no upper mediastinal metastases in tumors in the lower lobe.

The study investigated the efficacy and safety of a sex-selective lymph node strategy (no lower mediastinal lymph node clearance for upper lobe tumors and no upper mediastinal lymph node clearance for lower lobe tumors) in patients with 0.5 < CTR < 1 and ≤ 2 cm in diameter cT1N0M0 infiltrating NSCLC, aiming to more accurately assess the prognosis of the selective lymph node dissection strategy for nodes with 0.5 < CTR < 1 and ≤ 2 cm in diameter.