Table 1 shows demographic data and clinical baseline characteristics of a total of 151821 patients with hepatic metastases (80352 men and 71469 women, 1.12:1) were investigated. The median age was 67 years (IQR 58–76) and the median follow-up time was 3 months (IQR 1–11). Among them, 58.7% of the primary sites were derived from the digestive system, followed by the respiratory system (25.6%) and other sites (15.8%). Also, 80.4% of patients did not receive surgical-related interventions and 41.2% of patients had metastases in other sites, such as the lungs, bones, or brain. Other specific information is shown in Table 1.
Distribution of the primary site
Table 2 shows number and percentage of the specific distribution of the primary site, in which there were no patients with hepatic metastasis in myeloma and leukemia. At the same time, we conducted a subgroup analysis based on sex and age. Ten leading primary sites for the hepatic metastasis by sex and age were arranged in order, as shown in Figure 1.
In general, the ten leading primary sites for hepatic metastases were lung and bronchus (25.4%), colorectum (24.1%), pancreas (19.8%), stomach (4.5%), breast (4.1%), gallbladder and biliary system (3%), esophagus (2.7%), kidney and renal pelvis (2.1%), ovary (1.8%), and primary sites unknown (2%), which account for 89.5% of the total (Figure 1A). The lung, colorectum, and pancreas were the mostly common primary sites of hepatic metastasis, accounting for 69.3%.
From a sex perspective, in men, the five leading primary sites for hepatic metastases were lung and bronchus (26.4%), colorectum (25.4%), pancreas (20.2%), stomach (5.9%), and esophagus (4.3%) (Figure 1B). However, in women, the five leading primary sites for hepatic metastases were lung (24.3%), colorectum (22.6%), pancreas (19.3%), breast (8.7%), and ovary (3.8%). It is important to note that organs associated with sexual characteristics, such as the breast, ovary, and uterus were relatively common (Figure 1C). In addition, the esophagus and kidney were more common in men than the gallbladder and biliary tract, but this trend was opposite in women.
In terms of age, the primary sites of patients of different ages varied greatly. The most common primary sites for patients younger than 45 years were colorectum (36.2%), breast (12.7%), pancreas (10.1%), and genital organs (ovaries, uterus, and male or female genital organs) (Figure 1D). The primary sites common to patients younger than 65 years were the colorectum (27%), lung and bronchus (22.9%), and pancreas (18.2%) (Figure 1E). In patients aged 65 years or older, the common primary sites were the lung and bronchus (28.5%), pancreas (21.6%), and colorectum (21.2%) (Figure 1F). With increasing age, the proportion of primary sites of colorectal, breast, and genital system decreased, but the proportion of pancreas, lung and bronchus, gallbladder, and biliary system gradually increased.
Prognosis of patients with hepatic metastases
Table 3 shows the 1-year OS of patients with hepatic metastases at each primary site. The overall survival rates of patients with hepatic metastases at 6 months, 1 year, and 3 years were 44.5%, 28.7%, and 9.9%, respectively, with a median survival time of 4 months (Figure 2A). The prognosis of hepatic metastases from lymphoma (Hodgkin and non-Hodgkin), small intestine, genital system (breast, ovary, and other male or female genital organs), retroperitoneal tissues, and colorectum and anus was relatively better. The prognosis of hepatic metastases from primary sites unknown, urinary system (bladder, urethra), lung, pancreas, hepatobiliary system, and esophagus was quite poor (Supplementary Figure 1).
Table 4 shows the risk factors for the prognosis of hepatic metastases. Through Cox univariate and multivariate analysis, we found that sex, age, marital status, ethnicity, primary site, grade, presence of surgery, and presence of combined metastases were independent risk factors for prognosis. Figure 2 shows the Kaplan-Meier survival curves for patients with hepatic metastases under different conditions. Supplementary Figure 2 shows a forest plot based on univariate Cox regression analysis of the effects of surgery on the prognosis of each primary site. Most of hepatic metastases benefitted from surgical intervention at the primary site, except for the anus, non-Hodgkin lymphoma, prostate, eye and orbit, and other nonepithelial skin except melanoma of the skin.