2.4. Postoperative follow up

Abdominal ultrasound, contrast-enhanced computed tomography (CT) and/or magnetic resonance imaging (MRI), liver function test, and serum tumor markers level were performed every month for the first 3 months and then every 3 months for the initial 2 years. Telephone follow-up was conducted by a research nurse every month to update the survival status of patients. Overall survival time was defined from the date of operation to the date of death for any reason, or to the date of last follow-up in February 2020.