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

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.

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.

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.

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.