1540 Background: We have investigated the individualized benefit of CT screening as Anti-Lung Cancer Association projects (presented at ASCO 2006–2008). However, there has not been enough information about the relationship of lung cancer stage to tumor size in repeated CT screening. Therefore, we evaluated the stage-size relationship of these asymptomatic lung cancer cases diagnosed by long-term repeated screening with low-dose helical CT. Methods: Among 2,120 participants (mean age 63 years, 87% male, and 83% smoker) at baseline screening, 1,877 underwent semiannually repeated screening from 1993 to 2004. Nineteen (0.90%) prevalence cancers and 57 (0.32%) incidence cancers were detected. Within categories of tumor size, the distribution of pathological stage, histology, lymph node status, and distant metastases was determined. Results: Pathological stage has a strong relationship to tumor size at baseline screening (spearman r = 0.63, p = 0.013) and repeated screening (r = 0.65, p < 0.001). In the analysis of all 76 cases, lymph node status (r = 0.59, p < 0.001) and distant metastases (r = 0.55, p = 0.005) have also a strong relationship to tumor size. The percentages of cases with no metastases (N0M0) were 100% (0/21), 89% (17/19), 62% (8/13), 83% (10/12), 50% (4/8), and 33% (1/3) for the categories 10 mm or less, 11 mm to 15 mm, 16 mm to 20 mm, 21 mm to 30 mm, 31 mm to 40 mm, and 41 mm or greater, respectively. Histology for the categories 15 mm or less was localized bronchioloalveolar carcinoma in 13 cases, adenocarcinoma with mixed subtype in 11 cases, invasive adenocarcinoma in five cases, other non-small cell carcinoma in 10 cases, and small cell carcinoma in one case. Accumulated 10-year hazard ratio of above histology was 2.4, 2.5, 2.6, 4.1, and 0.7. In multivariate analyses, pathological stage was related to only tumor size (standardized regression coefficient beta = 0.59, p < 0.001) whereas histology was related to tumor size (beta = 0.43, p < 0.001) and smoking index (beta = 0.28, p = 0.016). Conclusions: These results provide direct evidence of a stage-size relationship in long-term repeated CT screening for lung cancer. Furthermore, early detection of lung cancer of 15 mm or less in diameter leads to the detection of early-stage (N0M0) lung cancer in repeated CT screening. No significant financial relationships to disclose.
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