Histopathologic prognostic factors in resected colorectal lung metastases

Background. Pulmonary metastasectomy is a standard method of treatment for selective pulmonary metastases of colorectal cancer. However, the pathologic factors of metastatic lesions that affect survival and tumor recurrence after pulmonary resection are less well defined. The pathologic findings of colorectal pulmonary metastases have not been correlated with clinical outcome. The study was conducted to clarify the characteristics and identify the prognostic factors of the pulmonary metastases of colorectal cancer. Methods. Between July 1992 and November 2002, 89 patients underwent the complete resection of pulmonary metastases of primary colorectal carcinoma, and we pathologically reviewed the surgical specimens of 136 metastatic lesions from these patients. Results. There were no perioperative deaths. The overall 5-year survival rate was 61.4%. No clinical factors were associated with the outcome. The univariate analysis of pathologic factors revealed aerogenous spread with floating cancer cell clusters (ASFC) (p = 0.004), vascular invasion (p = 0.002), lymphatic invasion (p = 0.032), and pleural invasion (p = 0.037) to be prognostic factors. The multivariate analysis showed vascular invasion (p = 0.02) and ASFC (P = 0.02) to be independent prognostic factors. The 5-year survival rate of patients whose lesions were positive for both ASFC and vascular invasion was 24.7% and much poorer than in the patients with ASFC without vascular invasion (78.6%), vascular invasion but without ASFC (80.2%), and patients negative for both (93.3%) (p = 0.0002). Conclusions. The morphologic features of ASFC and vascular invasion at metastatic sites are prognostic factors for colorectal cancer patients who have undergone pulmonary metastasectomy.