Automatic Abstraction of Computed Tomography Imaging Indication Using Natural Language Processing for Evaluation of Surveillance Patterns in Long-Term Lung Cancer Survivors

PURPOSE Despite its routine use to monitor patients with lung cancer (LC), real-world evaluations of the impact of computed tomography (CT) surveillance on overall survival (OS) have been inconsistent. A major confounder is the absence of imaging indications because patients undergo CT scans for purposes beyond surveillance, like symptom evaluations (eg, cough) linked to poor survival. We propose a novel natural language processing model to predict CT imaging indications (surveillance v others). METHODS We used electronic health records of 585 long-term LC survivors (≥5 years) at Stanford, followed for up to 22 years. Their 3,362 post–5-year CT reports (including 1,672 manually annotated) were used for modeling by integrating structured variables (eg, CT intervals) with key-phrase analysis of radiology reports. Naïve analysis compared OS in patients with CT for any indications (including symptoms) versus those without post–5-year CT, as in previous studies. Using model-predicted indications, we conducted exploratory analyses to compare OS between those with post–5-year surveillance CT and those without. RESULTS The model showed high discrimination (AUC, 0.86), with key predictors including a longer interval (≥6-month) from the previous CT (odds ratios [OR], 5.50; P < .001) and surveillance-related key phrases (OR, 1.37; P 5 .03). Propensity-adjusted survival analysis indicated better OS for patients with any post–5-year surveillance CT versus those without (adjusted hazard ratio, 0.60; P 5 .016). By contrast, no significant survival difference was found (P 5 .53) between patients with any CT versus those without post–5-year CT. CONCLUSION Our model abstracted CT indications from real-world data with high discrimination. Exploratory analyses revealed the obscured imaging-OS association when considering indications, highlighting the model’s potential for future real-world studies. © 2025 by American Society of Clinical Oncology.