CT screening for lung cancer: significance of diagnoses in its baseline cycle

PURPOSE: The aim of this study was to assess the significance of Stage I diagnoses of lung cancer in the baseline cycle of screening for this disease, with special reference to the potential for overdiagnosis. METHODS: We reviewed all 69 cases of Stage I lung cancer diagnosis resulting from our baseline CT screening. Among these 69 cases of lung cancer, 24 presented as solid, 30 as part-solid, and 15 as nonsolid nodules. The extent to which these represented genuine malignancy was assessed by a panel of experts on lung pathology, and the "aggressiveness" of these cases was addressed by the criterion of the tumor's volume doubling time being less than 400 days. RESULTS: The expert panel confirmed all 69 cases as representing genuine malignancy. Among the 69 cases without evidence of metastases, the proportion that satisfied the aggressiveness criterion was 60/69=87%. The corresponding proportions by presentation as solid, part-solid, and nonsolid nodule were 23/24 (96%), 27/30 (90%), and 10/15 (67%), respectively. CONCLUSIONS: In baseline CT screening for lung cancer, overdiagnosis of the disease is uncommon, with cases presenting as a nonsolid nodule a possible exception to this.