Purpose: The aim of this retrospective study was to establish a new prognostic staging system for pulmonary metastases from colorectal carcinoma (CRC).
Methods: The baseline characteristics and outcomes on 352 CRC patients who underwent complete pulmonary resection were collected from 19 institutions by the Japanese Society for Cancer of the Colon and Rectum (JSCCR) Study Group (group A). The clinical and pathological factors were entered into a multivariate analysis to identify independent variables that were helpful for accurately predicting the long-term prognosis after pulmonary resection. Using the selected variables in group A, we developed a new prognostic staging system (PSS). The new PSS was examined in a validation study in a series of 841 patients from 110 institutions of the JSCCR by the 78th society of the JSCCR (group B).
Results: We evaluated four variables selected in the multivariate analysis: the number of pulmonary metastases, the distribution, the disease-free interval and the lymph node metastases of primary cancer in group A. Using these four variables, we developed a new PSS. This PSS was found to significantly predict the prognosis in group B.
Conclusions: Our new PSS was useful for the selection of patients suitable for pulmonary resection.