Table 1.

Definitions of key clinical parameters used in the study

Complete remission	Clinical status that is free of any residual primary liver tumor, intrahepatic recurrence, and extrahepatic nonpulmonary metastasis right before pulmonary metastasectomy
Partial response	Clinical status not meeting the criteria of complete remission and showing a stable or reduced tumor size in the liver
Distant metastasis-free interval	Interval between the date of the last treatment of HCC in the liver and the date of the first occurrence of lung metastasis; no metastatic disease elsewhere concurrently
Disease-free interval	Interval between the date of curative surgery of intrahepatic lesion and the date of the first occurrence of lung metastasis
Overall survival	Time from the initial pulmonary metastasectomy to the last follow-up date or death