Retrospective review of lung cancers diagnosed in annual rounds of CT screening.

OBJECTIVE: The purpose of this study was to review the records of patients with diagnoses of lung cancer in annual repeat rounds of CT screening in the International Early Lung Cancer Action Program to determine whether the cancer could have been identified in the previous round of screening.
MATERIALS AND METHODS: Three radiologists reviewed the scans of 104 lung cancer patients and assigned the findings to one of three categories: 1, cancer was not visible at previous CT screening; 2, cancer was visible at previous CT screening but not identified; 3, abnormality was identified at previous CT screening but not classified as malignant. Nodule size, nodule consistency, cell type, and stage at the previous screening and when identified for further workup for each of the three categories were tabulated.
RESULTS: Twenty-four (23%) patients had category 1 findings; 56 (54%) category 2; and 24 (23%) category 3. When diagnosed, seven (29%) category 1, 10 (18%) category 2, and four (17%) category three cancers had progressed beyond stage I. All cancers seen in retrospect were in clinical stage I at the previous screening. Category 1 cancers, compared with categories 2 and 3, had faster growth rates, were less frequently adenocarcinomas (29% vs 54% and 67%, p = 0.01), and were more often small cell carcinomas (29% vs 14% and 12%, p = 0.12).
CONCLUSION: Lung cancers found on annual repeat screenings were frequently identified in the previous round of screening, suggesting that review of the varied appearance and incorporation of advanced image display may be useful for earlier detection.