Chapter 119: Pulmonary Metastases: The Role of Surgical Resection

Introduction

Pulmonary metastasectomy refers to the resection of secondary pulmonary malignancy. Most patients who develop pulmonary metastases are not curable, owing to presentation with extrathoracic metastases and lack of effective systemic therapy. Although there are no prospective, randomized trials comparing pulmonary metastasectomy to medical therapy or observation, metastasectomy has gained wide acceptance for patients who present only with metastases to the lungs. Several retrospective studies demonstrate an apparent survival advantage in patients with secondary pulmonary malignancy who undergo complete resection, comparing survival after resection to historical data for unresected patients, for whom survival is poor.

An important study that assessed the long-term results of pulmonary metastasectomy was based on an analysis of the International Registry of Lung Metastases.¹ This collaborative project retrospectively reviewed 5206 cases of lung metastasectomy performed in several institutions. Patients with a single metastasis had a survival of 43% at 5 years, compared with 34% in those with two or three metastases, and 27% in those with four or more metastases. The most important determinant of survival, however, was resectability: the ability to achieve complete resection of all recognizable pulmonary metastases. The overall 5-year survival for patients who underwent complete resection was 36%, with a median survival of 35 months. In those patients who had undergone incomplete resection, the 5-year survival was only 13%, and the median survival was 15 months.¹ These findings suggest that surgical resection offers a survival advantage for some patients.

A prognostic model was also created to select those who would benefit most, including the parameters of resectability, disease-free interval (DFI), and the number of metastases. Four distinct prognostic groups were identified: group 1 is the resectable group with no risk factors (DFI > 36 months and single metastasis); group 2 is the resectable group, with one risk factor (DFI < 36 months or multiple metastases); group 3 is the resectable group, with two risk factors (DFI < 36 months and multiple metastases); and group 4 is the unresectable group. Median survival was 61 months for group 1, 34 months for group 2, 24 months for group 3, and 14 months for group 4.¹ This prognostic model was presented as a reasonable guide to select patients for surgery.

In general, to be considered for pulmonary metastasectomy patients must fit the following criteria: the primary disease is controlled (or controllable); there is no other distant disease; complete resection of pulmonary involvement is achievable with adequate pulmonary reserve; and there are no effective medical therapies. For pulmonary metastasectomy to have survival value, the primary tumor itself must be controlled or controllable. If the pulmonary metastases are recognized metachronously, the site of the primary tumor is examined to exclude local recurrence. If the pulmonary disease has presented synchronously, the primary tumor is assessed and a decision is made regarding management. If no other metastatic disease is present, staged resection of the primary tumor and the pulmonary nodules ...