Identification of small lung nodules at autopsy: implications for lung cancer screening and overdiagnosis bias

Purpose: Unsuspected cases of lung cancer are reported to be uncommon in au topsy series, and these data have been used to suggest that indolent turner s are rare and that overdiagnosis bias is not an important factor in lung c ancer screening. The purpose of this study was to determine if a retrospect ive autopsy review is indeed accurate in identifying all small lung nodules on CT, and thus provide a true estimate of unsuspected lung tumors. Materi als and Methods: We identified all 1047 patients who had an autopsy at our institution from 1994 to 1998. We then reviewed the patients radiology reco rds and found 187 patients with a thoracic CT within 2 months of the postmo rtem examination. All 187 CT reports were reviewed in order to identify pat ients with at least one pulmonary nodule. CT studies with reports that desc ribed a nodule(s) were then re-reviewed to confirm presence and location of the nodule(s). The CT findings were than compared to the autopsy report to determine if the postmortem examination indeed found the nodule(s). Result s: 28 autopsy patients had at least one pulmonary nodule identified on thei r thoracic CT no more than 2 months before death. Nineteen patients (68%) h ad nodule(s) recorded on the autopsy report, two (similar to 10%) of which proved to have undiagnosed squamous cell carcinoma. Nine patients (22%) had no mention of pulmonary nodules seen on the CT recorded on their autopsy r eport. Conclusions: This study suggests autopsies do not identify all small pulmonary nodules found at CT. The true incidence of clinically insignific ant lung cancer is thus uncertain, and overdiagnosis bias in lung cancer sc reening may be more important than previously recognized. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.