Background: Chest computed tomographic (CT) scans frequently detect indeterminate pulmonary nodules (IPNs) in patients with colorectal cancer. The discovery of such nodules creates a clinical dilemma.
Purpose: This study was performed to identify clinical characteristics of IPNs and develop a predictive model to predict the risk of progression to pulmonary metastases in patients with colorectal cancer.
Methods: We analyzed data from a prospectively collected database involving 1195 patients with colorectal carcinoma who underwent curative surgery between January 2008 and June 2010. A predictive model was constructed on the basis of the probability risk score and validated in 115 patients collected from a separate treatment period.
Results: Of the 1195 patients who underwent a baseline staging chest computed tomography, 326 (27.2%) had IPNs. During a median follow-up of 26.7 months (interquartile range: 18.0-37.2), 74 (28.1%) showed pulmonary metastases. Five variables maintained prognostic significance after multivariate analysis: metachronous nodule, bilateral involvement, positive perineural invasion, increased number of positive lymph nodes, and rectal location of cancer. The 2-year progression-free survival rates for the very low-, low-, intermediate-, and high-risk groups were 96%, 82%, 46%, and 16%, respectively (P < 0.001), with a concordance index of 0.81 (95% confidence interval, 0.75-0.86). This model was validated in a separate patient set (P < 0.001), with a C-index of 0.83 (95% confidence interval, 0.77-0.88).
Conclusions: A predictive model for progression of IPNs may be clinically useful in discriminating patients who might benefit from an aggressive surveillance program and early pulmonary metastasectomies.