The recognition of pulmonary metastases from an extrathoracic primary tumor is a dramatic and emotional point in the care of a cancer patient. The clinical situation immediately changes from potential cure to the tacit acknowledgment of probable incurability. Goals of therapy change from living without evidence of disease to living, and living well, with systemic disease. We believe that pulmonary metastasectomy in carefully selected patients contributes to quality of life and affords these patients extended periods without obvious disease.
Many primary tumors metastasize to specific target organs. In the 1930s, it was noted that patients dying of pulmonary metastases frequently failed to exhibit extrapulmonary disease at autopsy. As a result, several surgeons believed that it would be reasonable to offer surgical resection of these lesions in the hope of prolonging patient survival. Interest in this surgical approach further increased with the development of systemic adjuvant chemotherapy, which appeared to increase patient survival rates.
The role of surgical resection of metastatic disease, however, is not universally accepted in the nonsurgical community. No randomized trial has been constructed to establish a survival advantage of pulmonary metastasectomy. In fact, the multitude of variables that would have to be included in the eligibility criteria (e.g., number of metastases, cell type, disease-free interval [DFI], cardiorespiratory reserve) make it challenging to design and complete an effective randomized trial of this nature. Without such data, however, many surgeons will remain appropriately skeptical that surgical resection might add significant benefit. Larger trials claiming improved survival after metastasectomy have been conducted in heterogeneous populations with tumors of mixed histologic types and mixed tumor doubling times. In such reports, patients who benefit the most from surgical resection appear to have a small tumor burden and a long doubling time (DFI); however, it is also these patients who may be able to survival long periods of time with their disease even without surgical resection. It can be hypothesized that a study population comprising slow-growing tumors in 40% of the subjects would have a 30% 5-year survival rate after surgery, and that same 30% would still be alive without an operation.
These arguments highlight the heterogeneity of this patient population and emphasize the need to tailor the surgical approach to each patient. Patients with dozens of metastases or rapid recurrence after a previous pulmonary metastasectomy will not gain major benefits from surgery. A very elderly patient with a slow-growing metastasis that would require pneumonectomy for resection would likely be better treated nonsurgically. These exceptions still leave many patients with pulmonary metastases that can be removed safely with an anticipated low morbidity and mortality.
A large volume of retrospective data is available to substantiate significant long-term survival of patients with pulmonary metastasectomy. When these data are compared with those of patients with pulmonary metastases who did not undergo metastasectomy, pulmonary metastasectomy can be interpreted to afford a distinct survival benefit, in addition ...