Treatment of advanced NSCLC (aNSCLC) is rapidly evolving, as new targeted and immuno-oncology (I-O) treatments become available. The iTEN model was developed to predict the cost and survival benefits of changing aNSCLC treatment patterns from a Canadian healthcare system perspective. This report describes iTEN model development and validation. Materials & methods: A discrete event patient simulation of aNSCLC was developed. A modified Delphi process using Canadian clinical experts informed the development of treatment sequences that included commonly used, Health Canada approved treatments of aNSCLC. Treatment efficacy and the timing of progression and death were estimated from published Kaplan-Meier progression free and overall survival data. Costs (2018 CDN$) included were: drug acquisition and administration, imaging, monitoring, adverse events, physician visits, best supportive care, and end-of-life. Results and conclusion: Clinical validity of the iTEN model was assessed by comparing model survival predictions to published real-world evidence (RWE). Four RWE studies that reported the overall survival of patients treated with a broad sampling of common aNSCLC treatment patterns were used for validation. The validation coefficient of determination was R 2 = 0.95, with the model generally producing estimates that were neither optimistic nor conservative. The model estimated that current Canadian practice patterns yield a median survival of almost 13 months, a five-year survival rate of 3% and a lifetime per-treated-patient cost of $110,806. Cost and survival estimates are presented and were found to vary by aNSCLC subtype. In conclusion, the iTEN model is a reliable tool for forecasting the impact on cost and survival of new treatments for aNSCLC. [1]. It is the leading cause of cancer-related mortality in Canada, accounting for approximately 26% of all cancer-related deaths [1]. Nonsmall cell lung cancer (NSCLC) is the most common form, representing approximately 80-85% of all lung cancers [2]. Approximately 50% of