The current status of tumor markers as biomarkers in the era of immunotherapy for hepatocellular carcinoma: alpha-fetoprotein alone is not sufficient

Introduction: Rapid development of systemic treatments has resulted in improved prognosis for unresectable hepatocellular carcinoma (uHCC) patients. Since immune therapy shows a favorable therapeutic efficacy, use of tumor markers as biomarkers for monitoring treatment response is necessary. This study aimed to elucidate changes in positive rates of 3 available tumor markers in Japan, including alpha-fetoprotein (AFP), des-gamma-carboxy prothrombin (DCP), and lens culinaris agglutinin-reactive AFP (AFP-L3) in uHCC patients treated with systemic therapies over time. Methods: From 2009 to 2023, 1470 uHCC patients with data of tumor markers before starting treatment were enrolled. The positivity cut-off value for AFP was 20 ng/mL, for AFP-L3 was 10%, and for DCP was 40 mAU/mL. After dividing the 15 years examined into three periods of five years each (period I, II, III), clinical features of the enrolled patients were evaluated, retrospectively. Results: The percentage of Barcelona Clinic Liver Cancer stage B patients who received systemic therapy increased from period I to III (27.7%, 38.5%, 46.6%, respectively, P<0.001), which was also seen for HCC patients with a non-viral etiology (alcohol and others) (29.9%, 39.7%, 49.6%, respectively P<0.001). Positive rates for AFP (67.8%, 62.1%, 50.8%, respectively) and DCP (84.1%, 80.5%, 72.7%, respectively) were decreased (each P<0.001), while the AFP-L3 rate did not show a significant change (54.4%, 57.7%, 51.9%, respectively P=0.390). Among the AFP-negative patients, the rate of positive for DCP or AFP-L3 was increased (24.4%, 28.1%, 35.4%, respectively, P=0.002). Conclusion: Based on introduction of systemic treatment in an early stage and increasing numbers of HCC cases with a non-viral etiology, the positive rate of AFP level has been declining. Thus, determination of DCP and AFP-L3 in addition to AFP as markers should be more actively utilized in clinical practice, as well as clinical trials for monitoring and evaluating treatment response in this era of combination immunotherapy as a powerful treatment.