8021 Background: The use of immune checkpoint inhibitors (ICIs) in lung cancer treatment, particularly in perioperative therapy, has significantly expanded. In Japan, atezolizumab was approved in 2022 for adjuvant therapy and nivolumab in 2023 for neoadjuvant therapy. Despite the long-term prognosis improvements associated with ICIs, their high costs have escalated healthcare expenses. This study evaluates the cost-effectiveness of perioperative therapies incorporating ICIs in Japan. Methods: A network meta-analysis (NMA) was conducted to derive hazard ratios (HRs) for disease-free survival (DFS) and overall survival (OS) from pivotal phase 3 clinical trials. Additionally, a partitioned survival model was developed to calculate quality-adjusted life years (QALYs) and life years (LYs). Cost data included drug and administration costs based on standard regimens. Results: ICIs with available DFS and OS data included atezolizumab, nivolumab, and pembrolizumab for adjuvant, neoadjuvant, and sandwich therapy, respectively. HRs (DFS/OS) compared to no perioperative therapy were as follows: adjuvant chemotherapy (0.81/0.86), neoadjuvant chemotherapy (0.87/0.80), adjuvant ICI (0.66/0.86), neoadjuvant ICI (0.55/0.49), and sandwich therapy (0.51/0.58). Cost/QALY/LY for each treatment were: no perioperative therapy (¥831,379/2.55/3.57), adjuvant chemotherapy (¥969,600/2.67/3.73), neoadjuvant chemotherapy (¥903,046/2.71/3.82), adjuvant ICI (¥9,209,863/2.70/3.74), neoadjuvant ICI (¥2,760,383/3.02/4.22), and sandwich therapy (¥8,235,047/2.95/4.10). Incremental cost-effectiveness ratios (ICERs) per QALY/LY were ¥425,189/¥295,036 for neoadjuvant chemotherapy and ¥6,152,576/¥4,592,090 for neoadjuvant ICI ($1 = \145). ICERs were not calculated for adjuvant chemotherapy, adjuvant ICI, and sandwich therapy due to extended dominance. Conclusions: In Japan, the general ICER threshold is ¥5,000,000, and ¥7,500,000 for treatments requiring special consideration, such as cancer therapies. The ICER for neoadjuvant chemotherapy was below the general threshold, and neoadjuvant ICIs below the special consideration threshold, making them cost-effective options for NSCLC patients in Japan. Other therapies were dominated, primarily due to 1) adjuvant chemotherapy being marginally more expensive and less effective than neoadjuvant chemotherapy, and 2) the high costs of long-term post operative ICI treatment for adjuvant ICI, and sandwich therapy.