BackgroundAlthough visceral pleural invasion, lymphovascular invasion, tumor spread through air spaces, and poor differentiation are pathological risk factors associated with unfavorable prognosis in patients with lung adenocarcinoma, the cumulative impact of these factors on prognosis remains unclear. MethodsWe enrolled 1532 patients with stage I lung adenocarcinoma. Patients were divided according to the number of risk factors as follows: Group A (without risk factors), Group B (one risk factor), and Group C (multiple risk factors). Moreover, we stratified patients into two subgroups based on tumor size (<= 3 cm, 3-4 cm). Kaplan-Meier analysis was used to evaluate 5-year disease-free survival (DFS) and overall survival (OS). ResultsOverall, 949, 404, and 179 patients were included in Groups A, B, and C, respectively. Group C had a larger tumor size and more cases of extrathoracic recurrence than the other groups. The 5-year DFS and OS gradually decreased across Groups A to C (DFS: 94.3%, 80.6%, and 64.3%, respectively, p < 0.001; OS: 97.2%, 92.7%, and 77%, respectively, p < 0.001). A similar trend was observed for tumors <= 3 cm in size (DFS: 95.2%, 83.2%, and 68.5%, respectively, p < 0.001; OS: 97.6%, 94.1%, and 79.6%, respectively, p < 0.001), but a less pronounced trend was observed for tumors between 3 and 4 cm in size (DFS: 72.1, 60.8, and 43.3%, respectively, p = 0.054; OS: 85.7, 82.1, and 64.7%, respectively, p = 0.16). ConclusionsPostoperative survival worsened with increasing pathological risk factors in patients with stage I lung adenocarcinoma, especially those with tumor size <= 3 cm.