Long-term results of a phase II clinical trial of superantigen therapy with staphylococcal enterotoxin C after microwave ablation in hepatocellular carcinoma.

Purpose: To prospectively evaluate safety and effectiveness of intratumoural injection of superantigen staphylococcal enterotoxin C (SEC) for hepatocellular carcinoma (HCC) after percutaneous microwave ablation (PMWA).
Methods: HCC patients (260) with tumours of 60 mm or less (average 29.2 ± 11.1 mm) that achieved technique effectiveness evidenced on imagings within one week of PMWA were enrolled. The SEC group consisted of 45 patients with 2000 U SEC injected into the marginal area of ablated tumour under ultrasound guidance on day 24, 28 and month 2, 5, and 7 after PMWA. The control group consisted of 215 patients receiving PMWA alone.
Results: The overall survival rates for 1, 3, and 5 years were 93.3%, 72.9%, 60.8% in the SEC group and 94%, 66%, 44.4% in the control group. The overall survival time had significant difference (p = 0.032). Treatment method was prognostic significance for overall survival on univariate (p = 0.045) and multivariate (p = 0.049) analyses. The disease-free survival time of the SEC group was longer than the control group (p = 0.195). The disease free survival rates at 1 and 3 years were 62% versus 56.6%, 37% versus 9.4% in the SEC and control subgroup of larger (D > 30 mm) tumours, and disease free survival time had significant difference (p = 0.032). Treatment method was a prognostic significance factor for disease free survival of larger tumours on univariate (p = 0.03) and multivariate (p = 0.023) analyses but was not for small tumours. No serious adverse event related to SEC injection happened.
Conclusions: Local superantigen injection at ablated HCC early after PMWA is safe, and achieves longer overall survival as well as disease free survival of larger tumours.