In recent years, the thoracic malignancies treatment landscape has become more complex with the emergence of novel targeted and immunotherapy-based treatments. Although beneficial to patients and physicians, this fast-paced therapeutic evolution has increased the complexity of clinical decision-making and amplified the importance of real-world evidence to support data from randomized controlled trials. The international I-O Optimise initiative was established in 2016 to provide real-world insights into the thoracic malignancies treatment landscape, and has since collaborated with 14 data sources across Europe and Canada, allowing access to data from ~ 500,000 patients with non-small-cell lung cancer, small-cell lung cancer, and malignant pleural mesothelioma. This article reviews pertinent I-O Optimise research, with discussion of the methodological/data-related learnings and expectations for future insights.