Sintilimab (PD-1 inhibitor) plus lenvatinib as conversion therapy followed by sequential surgery (SILENSES) for advanced unresectable hepatocellular carcinoma: a phase II, expansion trial.

Our previous findings demonstrated the promising antitumor activity and manageable safety of sintilimab-lenvatinib conversion therapy. The current study aimed to evaluate long-term survival outcomes in patients with unresectable hepatocellular carcinoma (HCC) who underwent sequential surgical resection after successful conversion therapy. In this prospective, single-arm, expansion, phase II trial, patients with unresectable HCC received lenvatinib plus sintilimab conversion therapy. Hepatectomy was performed in consenting patients after successful conversion therapy. The primary endpoint was the conversion rate; secondary endpoints included median overall survival (OS), 5-year survival rates, and recurrence-free survival (RFS). Successful conversion was achieved in 67 of 120 patients (56%, 67/120). Independent imaging review per mRECIST and RECIST v1.1 criteria demonstrated objective response rates of 58.3% (70/120) and 45.8% (55/120), respectively. With a median follow-up of 41.0 months (95% confidence interval [CI], 39.5-42.5) for the entire cohort, the median OS was 36.0 months (95% CI, 25.0 to not estimable [NE]), with a 5-year OS rate of 42.6% (95% CI, 34.0-53.0). Following multidisciplinary team evaluation and consideration of patient preferences, 60 patients underwent surgical resection, achieving a median RFS of 40.0 months (95% CI, 24.0 to NE) and a 5-year survival rate of 73.9% (95% CI, 62.7-87.1). Grade ≥3 treatment-related adverse events occurred in 37 patients (31%). Approximately half of the patients with unresectable HCC achieved successful conversion after sintilimab plus lenvatinib therapy. Among those who achieved successful conversion, subsequent curative surgery demonstrated not only a favorable safety profile but also significant survival benefits. Trial registration number: ChiCTR1900023914.