Adjuvant cytokine-induced killer cell immunotherapy in hepatocellular carcinoma: Extended follow-up of a randomized controlled trial and post-treatment immune cell profiling.

518 Background: Notwithstanding the pressing need for adjuvant therapy for hepatocellular carcinoma (HCC), most adjuvant therapies, including atezolizumab/bevacizumab, have failed. Meanwhile, adjuvant immunotherapy utilizing autologous cytokine-induced killer (CIK) cells for HCC improved recurrence-free survival (RFS) in a previously reported randomized controlled trial (RCT) and real-world data. This study aimed to assess the longer-term outcomes of the RCT and elucidate the underlying mechanisms of sustained effects of CIK cell treatment. Methods: This study comprised two parts: a long-term follow-up of the preceding RCT and an analysis of immune cells in patients who received adjuvant CIK cell treatment. In the original RCT, 226 patients who underwent curative treatment for stage I or II HCC were randomly allocated to either the CIK (n=114, 16 injections of 6.4×10 9 CIK cells over an 11-month period) or control group (n=112). The follow-up period was extended to 9 years after the enrollment of the last patient. The primary endpoint was recurrence-free survival (RFS). The secondary endpoints included cancer-specific survival (CSS) and overall survival (OS). Parallelly, a prospective study was conducted to investigate post-treatment changes of immune cells in peripheral blood of 7 patients, who received repeated transfer of CIK cells after curative treatment for HCC, using flow cytometry. Results: In the extended follow-up of the RCT (median follow-up=115.7 months, interquartile range=74.2–130.5 months), the CIK group sustained a significantly prolonged RFS (median=43.5 vs 27.4 months; hazard ratio [HR]=0.74, 95% confidence interval [CI]=0.55–0.99, P =0.045) and CSS (median=unreached; HR=0.49, 95% CI=0.25–0.95, P=0.04) compared to the control group. Adjuvant CIK cell therapy reduced the risk of overall death by 30%, although it did not achieve statistical significance (median=unreached; HR=0.70, 95% CI=0.44–1.11, P=0.1). A preliminary analysis of peripheral blood immune cells revealed that the CIK cell treatment tended to increase the frequencies of CD8 + and CD4 + classical memory cells. Conclusions: Adjuvant CIK cell treatment demonstrated significantly enhanced RFS and CSS in the prolonged follow-up of the RCT extending to 9 years in patients who received curative treatment for HCC. The CIK group also demonstrated a consistent trend of improved OS. The increase in memory T cell populations might be linked to the sustained off-treatment anti-tumor efficacy of CIK cell treatment.