The proportion of consolidation to ground-glass opacity on high resolution CT is a good predictor for distinguishing the population of non-invasive peripheral adenocarcinoma.

OBJECTIVE

If non-invasive lung carcinomas are distinguishable on computed tomography (CT), limited surgery can be indicated before operation as a radical procedure. The purpose of this study is to define high resolution CT (HRCT) findings that indicate pathologic T1N0M0 tumor without vessel invasion.

PATIENTS AND METHODS

We reviewed HRCT findings and pathological specimens of 98 consecutive patients underwent lobectomy or pneumonectomy with systematic hilar and mediastinal lymph node dissection from January 1996 to October 1999 for 101 pulmonary peripheral adenocarcinomas smaller than 3cm in diameter on HRCT. A total of 101 consecutive surgically resected peripheral adenocarcinomas of the lung measuring 3.0cm or less in the maximum dimension on HRCT were examined both radiologically and histologically. All CT scans ware reviewed by three chest radiologists or pulmonologists. The following parameters were measured on HRCT: the greatest diameter of tumor on found on all CT cuts (Td), the greatest diameter of consolidation found on all CT cuts (Cdmax), and the greatest diameter of consolidation found on a particular CT cut (Cd). Consolidation to tumor size ratio at respective maximum dimensions was calculated as Cdmax/Td, and consolidation to tumor size ratio on the slice image with the maximum tumor dimension was calculated as Cd/Td. One pathologist reviewed all pathological specimens to determine the size of tumor, evidence of vessel invasion, etc. without any information of HRCT, and we compared CT findings with pathological findings.

RESULTS

There was a statistically significant difference between tumors with pathologic T1N0M0 adenocarcinoma without vessel invasion (least invasive disease: LID) and tumors with lymph node involvement or vessel invasion (invasive disease: ID) in each parameter. However, only when tumors with Cdmax/Td smaller than 0.5 were selected as LID tumors, could ID tumors be eliminated from the LID group. Five-year survival rate of this population is 95.7%.

CONCLUSION

Consolidation to tumor size ratio at respective maximum dimensions was the best predictor of non-invasive peripheral adenocarcinoma.