Study Of Metastasis Risk Factors And Rules Of Mediastinal Lymph Node In Stage T1 Invasive Lung Adenocarcinoma

Objective: To analyze the metastasis risk factors and rules of mediastinal lymph node in T1 stage lung invasive adenocarcinoma,and provide a certain extent reference for surgeons on lymph nodes dissection.Methods: All patients who had underwent surgical treatment and pathologically diagnosed as stage T1(≤3cm)invasive adenocarcinoma were retrospectively selected in the department of thoracic surgery of China-Japan Union Hospital from January 2016 to June 2020.All patients underwent lobectomy or segmentectomy with systematic lymph node dissection or systematic lymph node sampling.The clinicopathologic and Imaging data of the patients were collected.Using SPSS 23.0 statistical software to analyze and compare the statistical data of patients between mediastinal lymph node metastasis(N2+)group and non-mediastinal lymph node metastasis(N2-)group,and the metastatic rule of mediastinal lymph node metastasis in N2+ patients was further analyzed.Results: 65(9.4%)patients had mediastinal lymph nodes metastasis(N2+),623(90.6%)patients had no mediastinal lymph node metastasis(N2-),including 40 patients with N1+ only and 583 patients with N0.There was no significant difference in the number of lymph node dissection between the N2+ group and the N2-group(P>0.05).Univariate analysis revealed tumor size,solid component,smoking history,preoperative CEA level,solid and micropapillary subtypes,Ki-67,preoperative lymph node status and infiltration of pleura,vessel,nerve and small bronchus are hazards for mediastinal lymph node involvement in clinical T1 invasive lung adenocarcinoma(P<0.05).Multivariate logistic regression indicated the size of nodule(OR value=2.149,95%CI=1.272-3.633,P=0.004),the proportion of solid components(OR value=4.284,95%CI=1.953-9.357,P<0.001),preoperative CEA level(OR value=3.108,95%CI=1.471-6.565,P=0.003),preoperative lymphadenopathy(OR value=3.242,95%CI=1.317-7.983,P=0.011),vascular nerve invasion(OR value=4.377,95%CI=2.019-9.488,P < 0.001),N1 lymph node involvement(OR value=5.735,95%CI=2.658-12.371,P<0.001)and micropapillary and solid subtypes(OR=2.92,95%CI=1.057-8.062,P=0.039)are independent risk factors for mediastinal lymph node metastasis.Among all N2 patients,16 patients(24.6%)had single-site skip metastasis(N2a1),24(36.9%)single-site non-skip metastasis(N2a2),and 25(38.5%)multi-site mediastinal lymph node metastasis(N2b).All patients with lesions located in the double upper lobe and right middle lobe did not have lymph metastasis in the lower mediastinum region(groups 8 and 9),and patients with lesions located in the double lower lobes all had lymphatic metastasis in the upper and lower mediastinum region on varying degrees,patients with lesions located in different lung lobes could have lymph node metastasis in group 7: 5 patients in double upper lobes(5/39),19 patients in double lower lobes(19/24),1 patient in right middle lobe(1/2).Conclusion: 1.The risk factors for mediastinal lymph nodes involvement in stage T1 invasive adenocarcinoma include larger lung nodule,especially for solid nodules,abnormal CEA levels and mediastinal lymph node enlargement on imaging,rapid freezing pathological judgment for weather N1 lymph nodes metastasis,micropapillary and solid subtypes,vascular nerve invasion.2.For patients with T1 invasive stage lung adenocarcinoma have high risk factors,the measure of mediastinal lymph node removement depends on which lung lobe the tumor locates.For bilateral upper lung lobes,the subcarinal and superior mediastinal lymph nodes should be removed,while for bilateral lower lung lobes,radical systematic lymph node dissection should be performed.