1056. Comparison of Lung Cancer Occurring in Fibrotic versus NonFibrotic Lung on Chest CT
Authors * Denotes Presenting Author
  1. Mary Salvatore *; Columbia University
Evaluate the behavior of lung nodules occurring in areas of pulmonary fibrosis and compare them to pulmonary nodules occurring in the nonfibrotic lung parenchyma.

Materials and Methods:
This retrospective review of chest CT scans and electronic medical records received expedited IRB approval and a waiver of informed consent. A total of 4,500 consecutive patients with a chest CT report containing the word fibrosis or a specific type of fibrosis were identified using the system M*Model Catalyst (Maplewood, MN). The largest nodule was measured in the longest dimension and reevaluated, in the same way, on the follow-up exam if multiple time points were available. The nodule doubling time was calculated. If the patient developed cancer, the histologic diagnosis was documented.

A total of 609 patients were found to have at least one pulmonary nodule on either the first or the second CT scan. The 274 largest pulmonary nodules were in the fibrotic tissue and 335 were in the nonfibrotic lung parenchyma. Pathology-proven cancer was more common in nodules occurring in areas of pulmonary fibrosis compared to nodules occurring in areas of nonfibrotic lung (34% vs 15%, p < .01). Adenocarcinoma was the most common cell type in both groups but more frequent in cancers occurring in nonfibrotic tissue. In the nonfibrotic lung, 1 of 126 (0.8%) of nodules measuring 1 - 6 mm were cancer. In contrast, 5 of 49 (10.2 %) nodules in fibrosis measuring 1 - 6 mm represented biopsy-proven cancer (p < .01). The doubling time for squamous cell cancer was shorter in the fibrotic lung compared to nonfibrotic lung, however, the difference was not statistically significant (p = .24). Fifteen incidental lung nodules on second CT obtained < 18 months after first CT scan was found in fibrotic lung and eight (53%) were diagnosed as cancer.

Nodules occurring in fibrotic lung tissue are more likely to be cancer than nodules in the nonfibrotic lung. Incidental pulmonary nodules in pulmonary fibrosis have a high likelihood of being cancer.