The Prognostic Influence Of Histological Subtypes Of Micropapillary Tumours On Patients With Lung Adenocarcinoma ≤2 Cm

Background:At present,lung cancer is the malignant tumor with the highest mortality rate in the world,of which non-small cell lung cancer（NSCLC）accounts for 80%-85%,and the most common histological type is adenocarcinoma.With the development of imaging technology and the widespread use of low-dose spiral CT,more and more small pulmonary nodules（≤2cm）are found clinically and confirmed as early lung adenocarcinoma in postoperative pathology.For resectable NSCLC,lobectomy and mediastinal lymph node dissection are still the main comprehensive treatment.According to the new classification proposed by the International Association for Lung Cancer Research（IASLC）,the American Thoracic Society（ATS）and the European Respiratory Society（ERS）,lung adenocarcinoma can be divided into five histological subtypes.According to related studies,lung adenocarcinoma dominated by acinar type shows a good prognosis,while micronipple-based lung adenocarcinoma is closely related to poor prognosis.Whether patients with micropapillary histological subtypes of lung adenocarcinoma can benefit from sublobectomy has not been studied,and the relationship between micropapillary components and lymph node metastasis is unclear.In this study,we aim to explore the value of micropapillary histological subtypes in predicting the specific surgical specificity and lymph node metastasis prognosis of early lung adenocarcinoma,and to select the best surgical scheme to bring accurate treatment for individualized treatment and prognosis stratification.Methods:This study retrospectively analyzed 1403 patients with NSCLC who underwent surgery in the Department of Thoracic surgery from January 2016 to December 2017.Inclusion criteria:1)patients with primary lung adenocarcinoma confirmed by postoperative pathology;2)tumor size≤2cm;3)postoperative pathological stage was p T_1-2N₀M₀（4）R0 resection.Exclusion criteria:1)received neoadjuvant therapy;2)patients with multiple nodules;3)incomplete medical records.Based on the above criteria,a total of 390 patients with NSCLC were included in this study.In this study,micronipple composition>5%was defined as group A,and micronipple composition≤5%was defined as group B.Patient observation measures included:sex,age,smoking history,preoperative complications,tumor site,maximum diameter of CT tumor,invasion of visceral pleura,operation method,lymph node dissection method,major pathological types,and survival data such as overall survival（OS）.SPSS26.0 statistical software was used for data analysis.The Chi-square test or Fisher’s exact test were used to compare the clinicopathologic data between the two groups.Kaplan-Meier survival curve analysis and Cox proportional hazards model were used to study the effect of micropapillary histological components on the survival of early stage lung adenocarcinoma≤2cm and the effect of different surgical methods and prognosis of patients after lymph node dissection.Results:The proportion of micropapillae subtype patients in group A was higher than that in group B,and the results were statistically significant（p<0.001）.Univariate and multivariate Cox regression analysis showed that micropapillae component was an independent risk factor affecting OS in patients with early lung adenocarcinoma≤2cm.The average OS of group A was 66.7 months.In the first,third and fifth-year OS rates were 98.8%,93.0%and 80.9%,respectively.The average OS of group B was 70.5 months.In the first,third and fifth-year OS rates were 99.3%,95.4%and 90.6%,respectively.OS in group B was significantly better than that in group A,with statistical significance（p=0.007）.Survival analysis of subtype patients with micropapillae components was conducted by different methods of lung surgery and lymph node dissection showed that only when the micropapillae component was greater than 5%,patients with OS after lobectomy and systematic lymph node dissection were significantly better than those with sublobectomy and limited lymph node dissection.When micropapillae component≤5%,there was no significant difference in survival.When the micropapillae component was>5%,the single factor OS was used to analyze the clinicopathological data of patients,and it was found that the OS of patients with micropapillae>5%was related to lymph node dissection and surgical method（p<0.05）.The COX model was used for multivariate analysis,and the results showed that only the surgical method was related to the OS of patients with micropapillae>5%（p=0.014）.Conclusion:The micropapillary histological component is an independent risk factor affecting OS in patients with early lung adenocarcinoma≤2cm.When the proportion of micropapillary components is different,the prognosis of patients is different with different surgical methods and lymph node dissection.Lobectomy and systematic lymph node dissection are recommended for patients with micropapillary histological composition＞5%;sublobar resection and limited lymph node dissection are recommended for patients with micropapillary histological composition≤5%.