Optimal Extent of Pulmonary Resection in Clinical Stage IA Non-Small Cell Lung Cancer

1. Background * The standard extent of pulmonary resection for non-small cell lung cancer (NSCLC) is still lobectomy. However, recent advances in imaging technology and staging modalities and the widespread use of computed tomography (CT) screening have greatly increased the probability of detecting small-sized tumors, especially with ground-glass opacity (GGO) feature. Adenocarcinoma with GGO feature generally has a good prognosis due to its minimally invasive nature. Many studies have shown that these pathologically less invasive subtypes are associated with better prognoses compared with other subtypes such as acinar, papillary, micropapillary, and solid predominant invasive adenocarcinoma. * This recent change in the disease pattern of NSCLC from locally advanced and solid tumors to early and less invasive tumors with GGO features have led to a resurgence of interest in sublobar resection. Several retrospective studies have been conducted to compare the early and late outcomes including long-term survival between patients who underwent lobectomy and those who underwent sublobar resection. * Multiple reports have suggested that small-sized peripheral lung adenocarcinoma can be treated by sublobar resection, yielding survival rates similar to those of lobectomy. Lobectomy is considered to be too much for these less invasive tumors and sublobar resection would be sufficient for these tumors. If sublobar resection is equivalent to lobectomy in terms of their oncologic efficacy for the surgical treatment of NSCLC, the potential benefits of sublobar resection include (1) the preservation of vital lung parenchyma and pulmonary function, which may lead to improved early morbidities and mortalities and then late quality of life and (2) a chance for a second resection with a subsequent primary NSCLC. * However, when considering the published evidence for sublobar resection, its interpretation needs to be cautious. Since most studies were non-randomized, there may also have been selection bias in terms of preoperative patient risk factors (intentional vs. compromised sublobar resection), tumors of various histological subtypes or different tumor size in the study arms. Therefore, the results from two randomized trials of lobectomy versus sublobar resection for small-sized lung cancer currently ongoing in Japan (Japan Clinical Oncology Group \[0802\]) and in the United States (Cancer and Leukemia Group B \[140503\]) need to be awaited. * Based on these clinical circumstances and the published evidence, the investigators developed the decision-making algorithm regarding the surgical treatment for clinical stage IA NSCLC. 2. Hypothesis The investigators hypothesized that selection of surgical procedure according to the pre-defined institutional decision-making algorithm will not compromise the treatment outcomes including overall survival and disease-free survival in patients with clinical stage IA non-small cell lung cancer. 3. Purpose The purpose of this study is to determine the outcome of participants with clinical stage IA NSCLC treated by 3 types of surgical resection (wide wedge resection, segmentectomy, or lobectomy) according to the institutional decision-making algorithm 4. Study plan The investigators are planning to enroll 1,000 participants who meet the pre-defined eligibility criteria over 5 years.