Comparison of the study groups at baseline
Baseline clinicopathological characteristics in the splenectomy and non-splenectomy groups were compared (Table 1). Patients in the splenectomy group were younger and more often female versus patients in non-splenectomy group (p=0.048 and 0.006, respectively). Patients undergoing splenectomy had better underlying liver function measured by Child-Pugh scores and the Model for End-stage Liver Disease (MELD) scores compared with non-splenectomy group (all p<0.05, Table 1). Although etiology of liver cirrhosis was similar between the two groups, high viral load (HBV DNA >1000 copy/ml) and antiviral treatments were more frequent in non-splenectomy versus splenectomy group (both p<0.05). Compared with patients who did not undergo a splenectomy, patients who had a splenectomy were likely to have severe pancytopenia, lower serum level of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin, but increased albumin (all p<0.01, Table 1). Of note pancytopenia resolved after splenectomy. Renal and coagulation function were no different between the two groups. Moreover, 53.6% (218/407) of patients in the splenectomy group had severe esophagogastric varices. In the surgery group, 88% (358/407) of patients underwent splenectomy and pericardial devascularization.
Development of HCC
Median follow-up time was similar in the surgery and control groups (63 [range, 8-103] and 62 [range, 12-104] months, respectively). The cumulative incidence of HCC development was much lower among patients who had a splenectomy versus individuals who did not (Hazard ratio [HR] 0.63, 95% confidence interval [CI] 0.44-0.90, p=0.005, Breslow=7.7) (Figure 1A). The cumulative HCC incidence at 1-, 3-, 5- and 7-years were 1%, 6%, 11% and 16% among patients undergoing splenectomy, and 2%, 10%, 17% and 24% among patients receiving medication treatment only, respectively.
Splenectomy and Risk of HCC
Overall survival of the patients in the two groups was comparable (splenectomy: 1-, 3-, 5- and 7-year survival 100%, 97%, 91% and 86% vs. no splenectomy: 100%, 97%, 92% and 84%; p=0.899)(Figure 2A). However, on cox proportional hazard regression modeling was several demographic, virus and liver-related factors were associated with development of HCC. Specifically, on univariate analysis, age, male gender, smoking, HBV DNA >1000 copy/ml were each associated with an increased risk of HCC, whereas splenectomy and anti-HBV treatment were associated with a lower incidence of HCC (all p<0.1, Table 3). On multivariate analysis, age and male gender remained associated with a higher incidence of HCC development, while patients with a history of splenectomy had a lower incidence of HCC (HR 0.55, 95% CI 0.32-0.95, p=0.031) (Table 3).
Propensity score matching (PSM) analysis utilizing variables such as age, gender, liver function, HBV and HCV titers, anti-HBV and anti-HCV treatments, diabetes, smoking and alcohol use was then performed. Specifically, 233 pairs of patients were generated in a matched cohort (Table 2). PSM confirmed that patients who underwent splenectomy had a lower incidence of HCC versus patients who did not undergo splenectomy (HR 0.53, 95% CI 0.31-0.91, p=0.028, Breslow=4.9) (Figure 1B). In fact, after PSM, the cumulative incidence of HCC at 1-, 3-, 5- and 7-years was 1%, 6%, 7% and 15% among patients who had a splenectomy versus 1%, 6%, 15% and 23%, respectively, among patients who did not undergo non-splenectomy.
Clinical outcomes of HCC patients
In total, 49 patients (12.0%) in the splenectomy group and 75 patients (16.2%) in the non-splenectomy group developed HCC during follow-up. While liver function and tumor status were comparable between the two groups, patients with HCC who had a previous splenectomy were less likely to undergo resection versus HCC patients in non-splenectomy group (12.2% vs. 33.3%, p=0.008) (Table 4). The utilization of the tumor-directed treatments (e.g. surgical resection, liver transplant, TACE and radiofrequency ablation) was similar among patients who had previously did or did not undergo a splenectomy (59.2% vs. 69.3%, respectively; p=0.246). In turn, overall survival of patients with HCC was not different in the splenectomy versus non-splenectomy groups (p=0.493, Figure 2B).