Incidence trends and surgical outcomes of synchronous liver metastasis across cancer types: a population-based cohort study

Background: Liver metastasis (LM) is commonly detected in a range of malignancies, but data on the incidence trends and efficacy of surgery are lacking. We aimed to assess incidence trends of synchronous LM in various primary cancers, and determine whether surgery is justified for such patients. Methods: This retrospective population-based cohort study utilized data from 17 US registries of the Surveillance, Epidemiology, and End Results (SEER) program (2010-2021). Age-standardized incidence rates and annual percentage changes were used to character the incidence trends. Propensity score matching and multivariable Cox proportional hazards regression models were performed to examine the effect of LM surgery on overall survival (OS). Results: Among 4,180,870 cancer patients, 249,946 (6.0%) developed synchronous LM. The most common primary sites of LM were colorectum (25%), lung (24%), and pancreas (21%). The absolute number of LM patients increased between 2010-2021, with incidence increasing by 2.24% annually in 2010-2014, then decreasing by 0.69% annually until 2021. Notably, incidence of LM from colorectum, esophagus, and pancreas rose, whereas LM from lung and bronchus declined. Patients aged 60-79 were the major population suffering from LM, while significant increases were observed in those aged 20-39. Nearly 47.5% of LM cases were oligometastatic liver metastasis (oLM), indicating no metastasis to other organs. More than half of LM from small intestine, pancreas, colorectum, and stomach cancers were oligometastatic, whereas prostate, bone, and skin cancers developed multi-organ metastasis rapidly. Patients with oLM who underwent surgery of metastasis typically showed improved OS than those who did not (median OS, 6 months versus 44 months; 5-year survival rates, 7.4% versus 41%), especially for oLM from colorectum, pancreas, and small intestine cancers. Conclusion: The overall burden of LM increased between 2010 and 2021. There were significant differences in incidence trends, metastatic patterns, and surgical effectiveness of LM across various primary cancer types.