Drs. Dresler and Goldberg review the role of resection of metastatic tumors to the lung. It is a difficult topic, with the exception of osteosarcoma, for which the practice of secondary resection is common and clearly of benefit. For lung metastases from other tumors, however, the use of resection is based largely on sporadic and anecdotal reports.
Patients with osteosarcoma are usually followed by strict protocols, often in major sarcoma centers, and the vast majority of such patients with lung metastasis are identified early in the course of metastatic disease. About 15% to 20% of patients with osteosarcoma present with metastatic lung disease; these individuals have a much lower salvage rate than the 25% to 35% of patients relapsing after neoadjuvant or adjuvant chemotherapy and surgical control of the primary site. The only sites involved in these patients are distant bone and the local site. The information available for this group includes virtually all such patients, and the salvage rates for pulmonary resection in centers with large sarcoma practices are remarkably similar.
In the case of epithelial malignancies, very little literature exists other than anecdotal reports from centers with large thoracic surgical services. The number of patients who must be screened for metastatic disease limited to the lung is unknown, but this is certainly a very uncommon event in patients with epithelial malignancies. The authors' contention that 20% to 25% of patients dying with metastatic disease to the lung will be free of metastasis elsewhere is based on a small autopsy series done more than 60 years ago and is not likely to be valid today.
Many questions remain with regard to surgical resection of both metastatic disease of osteosarcoma and epithelial malignancies with limited, surgically treatable metastases. Probably the most exciting recent development is the role of adjuvant (chemo)therapy for such patients. Given that the majority of patients in the western world who develop cancer today will have a primary from the lung, breast, or colon, for which adjuvant or neoadjuvant therapy may be of benefit, the obvious question of whether such therapy should be used in patients destined for resection should be considered and should be the basis of clinical trials.
In the case of osteosarcoma, breast cancer, and colon cancer, adjuvant chemotherapy has clearly been of benefit in eradicating micrometastatic disease. The role of further adjuvant therapy is unclear. However, few patients with osteosarcoma ever undergo only one thoracotomy, suggesting that micrometastatic disease is still present.
Obviously, a number of factors must be considered in such patients, in addition to the pulmonary factors detailed by Drs. Dresler and Goldberg. These include control of the primary tumor, the interval between development of the primary and metastatic lesion, and prior treatment, as well as the age of the patient.
Solitary metastases or even multiple but resectable metastases limited to the lung are uncommon feature of both breast and colon cancer, however. Nevertheless, they do occur, and Drs. Dresler and Goldberg suggest an excellent starting place for what hopefully may become a national or international trial.