Cavallaro P, Bordeianou L, Stafford C, et al. - Using National Cancer Database, researchers analyzed the impact of primary tumor site on overall survival in stage IV colorectal cancer (CRC) individuals with single-organ metastases to the liver or lung, as well as described the prognostic significance of commonly tested genetic variants like KRAS mutation and microsatellite instability (MSI) in this population. Between 2010 and 2014, they identified 38,328 patients with CRC presenting with synchronous metastases to the liver or lung. On unadjusted analysis, median survival was significantly longer for patients with lung metastases vs liver metastases for left-sided (27 vs 25 months) and right-sided CRC (19 vs 15 months), on the other hand, rectosigmoid and rectal cancers displayed no variation. Patients with liver metastases showed worse survival vs lung metastasis on multivariate analysis. Findings suggested that primary tumor site has an impact on overall survival for patients with single-organ metastases to the liver or lung. In addition, in selected individuals with single-organ metastases, KRAS mutation and MSI status are of prognostic importance.