Staging Chest CT in Patients With Early-Stage Colon Cancer: Analysis of Impact on Survival Using Inverse Probability Weighting and Causal Diagram.

Please see the Editorial Comment by Carlos Zamora discussing this article. Staging chest CT in patients with early-stage colon cancer has been shown to have negligible diagnostic yield for detecting lung metastases. Nonetheless, staging chest CT may have potential survival benefits, including opportunistic screening of comorbidity and provision of a baseline examination for future comparisons. Evidence regarding the impact of staging chest CT on survival in patients with early-stage colon cancer is lacking. To determine whether the performance of staging chest CT affects survival in patients with early-stage colon cancer. This retrospective study included patients with early-stage colon cancer (defined as clinical stage 0 or I on staging abdominal CT) at a single tertiary hospital between January 2009 and December 2015. Patients were divided into two groups according to the presence of staging chest CT. To ensure comparability between the two groups, inverse probability weighting was applied to adjust for the confounders derived from a causal diagram. The between-group differences in adjusted restricted mean survival time at 5 years were measured for overall survival, relapse-free survival, and thoracic metastasis-free survival. Sensitivity analyses were performed. A total of 991 patients (618 men, 373 women; median age, 64 years [IQR, 55-71] years) were included: 606 (61.2%) patients had staging chest CT. For overall survival, the difference between groups in restricted mean survival time at 5 years was not significant (0.4 months [95% CI: -0.8, 2.1 months]). The differences between groups in restricted mean survival time at 5 years were also not significant for relapse-free survival (0.4 months [95% CI: -1.1, 2.3 months]) and for thoracic metastasis-free survival (0.6 months [95% CI: -0.8, 2.4 months]). Similar results were observed in sensitivity analyses testing 3-year survival differences, testing 10-year survival differences, excluding patients who underwent FDG PET/CT during staging workup, and adding treatment decision (surgery vs no surgery) to the causal diagram. The use of staging chest CT did not affect survival in patients with early-stage colon cancer. Staging chest CT may be omitted from the staging workup in patients with colon cancer of clinical stage 0 or I.