Indeterminate pulmonary nodules in colorectal cancer.

Aim: To investigate the clinicopathologic parameters of pulmonary metastasis in colorectal cancer (CRC) patients after lung operation of indeterminate pulmonary nodules (IPNs).

Methods: From a prospective database of CRC patients, 40 cases that underwent lung operation between November 2008 and December 2012 for suspicious metastatic pulmonary nodules on chest computed tomography (CT) were enrolled. The decision to perform a lung operation was made if the patient met the following criteria: (1) completely resected or resectable primary CRC; (2) completely resectable IPNs; (3) controlled or controllable extrapulmonary metastasis; and (4) adequate general condition and pulmonary function to tolerate pulmonary operation. Lung operation was performed by a thoracic surgeon without CT-guided biopsy for pathologic confirmation.

Results: A total of 40 cases of lung resection was performed in 29 patients. Five patients underwent repeated lung resection. The final pathology result showed metastasis from the CRC in 30 cases (75%) and benign pathology in 10 cases (25%). The primary tumor site was the rectum in 26/30 (86.6%) cases with pulmonary metastasis, but only 3/10 (30%) cases in the benign group had a primary rectal cancer (P = 0.001). Positron emission tomography (PET)-CT was performed for 22/30 (73.4%) patients in the lung metastasis group and for 6/10 (60.0%) patients in the benign group. PET-CT revealed hot uptake of (18)fluorine 2-fluoro-2-deoxy-D-glucose with all IPNs in both groups. The group with pulmonary metastasis had a higher incidence of primary rectal cancer (P = 0.001), a more advanced tumor stage (P = 0.011), and more frequent lymphatic invasion of tumor cells (P = 0.005). Six cases with previous liver metastasectomy were present in the lung metastasis group. Serum carcinoembryonic antigen levels before lung operation were not elevated in any of the patients.

Conclusion: The stage and location of the primary tumor and tumor cell infiltration of lymphatics provide useful indicators for deciding on lung resection of IPNs in CRC.