Survival and Prognostic Factors of Isolated Pulmonary Metastases Originating from Colorectal Cancer: An 8-year Single-center Experience

Background: Isolated pulmonary metastasis (IPM) is a rare entity that accounts for 10% of pulmonary metastases seen in colorectal cancer (CRC). This study aims to evaluate the overall 5-year survival of IPM originating from CRC and identify potential prognostic factors affecting the overall survival (OS).

Methods: A retrospective cohort study conducted in a tertiary care center. The study included all patients diagnosed with CRC aged 18-75 years who underwent primary tumor resection with curative intent between 2008 and 2015, and developed IPM. Patients with no follow-up and those with extra-pulmonary metastases were excluded.

Results: The prevalence of IPM in the overall CRC cases was 4.18% (20/478 patients). The mean age of patients with IPM was 52.7 ± 12.9 years. Ten patients had synchronous IPM (50%), thirteen had unilateral (65%), and eleven underwent metastasectomy (55%). The 5-year OS was 40%, and the mean OS was 3.12 ± 1.85 years. Several factors were found to be associated with a favorable outcome, which include unilateral IPM (3.69 vs. 2.07 years; P = 0.024), metachronous (4.25 vs. 2.14 years; P = 0.017), metastasectomy (4.81 vs. 1.83 years; P = 0.005). In addition, mortality was likely to be decreased by more than 90% after metastasectomy (unadjusted odds ratio = 0.071; 95% confidence interval [CI] = 0.01-0.8; P = 0.032).

Conclusions: Forty percent of the included patients survived the 5-year follow-up. Better survival was associated with the metastases being unilateral, metachronous, and metastasectomy. Mortality was lower in patients with pulmonary recurrence after metastasectomy.