Discrepancy of computed tomographic image between lung and mediastinal windows as a prognostic implication in small lung adenocarcinoma

Background There have been no proven preoperative indicators for postoperative survival of patients with an adenocarcinoma, the incidence of which has been increasing lately. Methods Of 952 consecutive patients operated on for primary lung cancer between 1995 and 2002, 167 patients with a proven adenocarcinoma 3 cm or less in diameter underwent complete removal of the primary tumor. We examined their computed tomographic scans to estimate tumor shadow disappearance rate (TDR), which was defined as the ratio of the tumor area of the mediastinal window to that of the lung window, reviewed the clinical records, and evaluated their relation to prognosis. Results On univariate analyses, size of the tumor (p = 0.0380), TDR (p = 0.0018), carcinoembryonic antigen (p = 0.0001) pathologic stage (p< 0.0001), nodal involvement (p< 0.0001), lymphatic invasion (p = 0.0001), and vascular invasion (p = 0.0017) were significantly associated with prognosis. Also, the outcomes of multivariate analyses for preoperative factors indicated that TDR (p = 0.0340) and carcinoembryonic antigen (p = 0.0047) are significant independent prognostic determinants. The 5-year survival was 48% in cases with a TDR of 0% to 25%, 87% in those with a TDR of 26% to 50%, 97% in those with a TDR of 51% to 75%, and 100% in those with a TDR of 76% to 100%. The incidence of lymphatic, vascular invasion, and nodal metastases was lower in patients with a higher TDR. Conclusions Small-sized adenocarcinomas with a higher TDR showed less lymphatic, vascular vessel invasion, or nodal involvement, and demonstrated longer survival, suggesting that TDR was associated with clinical-pathologic characteristics and tumor aggressiveness. Preoperative assessment of TDR may be useful to identify an appropriate candidate for a lesser pulmonary resection.