Past, present, and future perspectives of pulmonary metastasectomy for patients with advanced colorectal cancer.

Over a half-century has passed since Thomford et al. proposed the selection criteria for pulmonary metastasectomy, and several prognostic factors have been identified. Although screening modalities and operations have changed dramatically, the important concepts of the selection criteria remain unchanged. Recent improvements in the survival outcomes of colorectal cancer patients undergoing pulmonary metastasectomy may be the result of strict adherence to the selection criteria for oligometastatic lung tumors, which can mimic local disease. Pulmonary metastasectomy has become an important option for selected patients with oligometastasis, based mainly on a large amount of retrospective data, but its effect on survival remains unclear. Curable pulmonary metastasis might be regarded as a "semi-local disease" under the spontaneous control of an acquired alteration in host immune status. The current practice of pulmonary metastasectomy for colorectal cancer focuses on selecting the most appropriate operation for selected patients. However, in the rapidly evolving era of immunotherapy, treatment-naïve patients for whom surgery is not suitable might be pre-conditioned by immunotherapy so that they may be considered for salvage surgery.