Thymostimulin in advanced hepatocellular carcinoma: A phase II trial

BACKGROUND: Thymostimulin is a thymic peptide fraction with immune-mediated cytotoxicity against hepatocellular carcinoma in vitro. In a phase II trial, we investigated safety and efficacy including selection criteria for best response in advanced or metastasised hepatocellular carcinoma. METHODS: 44 patients (84 % male, median age 69 years) not suitable or refractory to conventional therapy received thymostimulin 75 mg subcutaneously five times per week for a median of 8.2 months until progression or complete response. 3/44 patients were secondarily accessible to local ablation or chemoembolisation. Primary endpoint was overall survival, secondary endpoint tumor response or progression-free survival. A multivariate Cox's regression model was used to identify variables affecting survival. RESULTS: Median survival was 11.5 months (95% CI 7.9–15.0) with a 1-, 2- and 3-year survival of 50%, 23% and 9%. In the univariate analysis, a low Child-Pugh-score (p = 0.01), a low score in the Okuda- and CLIP-classification (p < 0.001) or a low AFP-level (p < 0.001) were associated with better survival, but not therapy modalities other than thymostimulin (p = 0.1) or signs of an invasive HCC phenotype such as vascular invasion (p = 0.3) and metastases (p = 0.1). The only variables independently related to survival in the Cox's regression model were Okuda stage and presence of liver cirrhosis (p < 0.01) as well as response to thymostimulin (p < 0.05). Of 39/44 patients evaluable for response, two obtained complete responses (one after concomitant radiofrequency ablation), five partial responses (objective response 18%), twenty-four stable disease (tumor control rate 79%) and eight progressed. Median progression-free survival was 6.4 months (95% CI 0.8–12). Grade 1 local reactions following injection were the only side effects. CONCLUSION: Outcome in our study rather depended on liver function and intrahepatic tumor growth (presence of liver cirrhosis and Okuda stage) in addition to response to thymostimulin, while an invasive HCC phenotype had no influence in the multivariate analysis. Thymostimulin could therefore be considered a safe and promising candidate for palliative treatment in a selected target population with advanced hepatocellular carcinoma, in particular as component of a multimodal therapy concept. TRIAL REGISTRATION: Current Controlled Trials ISRCTN29319366.