Many retrospective series on pulmonary metastasectomy report overall 5-year survival rates of 30% to 40%.6,27 Data from the International Registry of Lung Metastases showed that after complete resection, the 5-year survival was 33% for patients with a DFI of 0 to 11 months after control of the primary malignancy and 45% for those with a DFI greater than 36 months. For single lesions, the 5-year survival was 43%, and it was 27% for four or more lesions. Global overall survival was 36% at 5 years, 26% at 10 years, and 22% at 15 years after complete resection. These data represent the gamut of epithelial, sarcoma, melanoma, and germ cell tumors, for which the benefit of resection will depend on specific tumor histology (Fig. 78-4)6. The literature on cell type-specific experience with pulmonary metastasectomy is growing.
Survival of patients following complete resection according to four major tumor types: epithelial, sarcoma, germ cell, and melanoma. (Reproduced with permission from Pastorino U, Buyse M, Godehard F, et al. Long-term results of lung metastasectomy: prognostic analyses based on 5206 cases. The International Registry of Lung Metastases. J Thorac Cardiovasc Surg. 1997;113:37–49; Fig. 4.)
Although several new chemotherapeutic agents have shown promising effects on systemic metastases, no standard chemotherapy has been found to improve survival significantly in patients with colorectal metastases to the lung. Encouraging surgical results have led to the acceptance of aggressive surgical management. The overall 5- and 10-year survival rates are approximately 35% to 45% and 20% to 30%, respectively.41–45 Important prognostic factors include number of pulmonary metastases, carcinoembryonic antigen level, and regional lymph node involvement.17
Pulmonary resection for renal cell metastases can offer a 20% to 50% 5-year survival.24,46,47 Larger number and size of nodules, increasing number of lymph node metastases, shorter DFI, and decreased preoperative forced vital capacity are predictive risk factors for death in this population.24
The advent of effective chemotherapy has changed the management of pulmonary metastases of germ cell tumors dramatically, and chemotherapy is now the first line of treatment. Surgical resection has been relegated to an adjuvant form of therapy and is reserved for patients who have a complete serologic response to chemotherapy with normalization of serum tumor markers and residual primary lesions. Although surgery may benefit patients who have had a decrease in serum markers shy of complete normalization, the patient with continued elevation of markers is likely better served with a change in chemotherapy. For most patients with germ cell cancers, pulmonary resection is no longer used as primary treatment.
Cisplatin-based chemotherapy is essential as initial treatment for nonseminomatous testicular cancer. Pathologic findings of mature teratoma or necrosis in resected pulmonary metastases indicate good prognosis, with only a 5% to 10% relapse rate. Pulmonary resection is used both diagnostically and therapeutically to determine whether active microscopic disease is still present after normalization of tumor markers and to remove residual mature teratoma. The 5-year survival rate for patients who have these tumors is 68% to 82% after pulmonary metastasectomy.48
Sarcoma has a natural tendency to metastasize to the lungs. Isolated pulmonary sarcoma metastases occur in 23% to 54% of patients with sarcoma.49 Pulmonary metastasectomy is an important method of therapy since most sarcomas are relatively chemoresistent. Several retrospective studies have established 3-year survivals of 20% to 54% for patients with surgical resection of sarcoma lung metastases.50 Sarcomas are a heterogeneous group with over 50 different histologic subtypes. Among patients with soft-tissue sarcoma that develop pulmonary metastases, the most common histologic findings include malignant fibrous histiocytoma, synovial sarcoma, and leiomyosarcoma.51
Operative resection is the only potentially curative treatment for patients with thoracic metastases from osteogenic sarcoma. After the primary tumor has been resected, routine adjuvant chemotherapy can improve the disease-free survival and decrease the burden of metastatic pulmonary disease.52 The 5-year survival for pulmonary metastases is related to the timing of appearance with respect to the initiation of chemotherapy. Survival when lesions are detected after completion of chemotherapy is significantly better than with the appearance of metastases during chemotherapy.53 Global 5-year survival rates after pulmonary metastasectomy range from 20% to 50%.23,28
Soft-tissue sarcomas are notoriously resistant to chemotherapy and almost always metastasize solely to the lungs. Surgery remains the only potential curative treatment, and the median survival after diagnosis of pulmonary metastases without surgery is 15 months. Reported 5-year survival rates after pulmonary metastasectomy for soft-tissue sarcoma range from 25% to 35%.54,55 Factors associated with improved survival among different reports include prolonged DFI, low-grade tumor, young age, slow tumor doubling time, low number of nodules, histology of malignant fibrocystic histiocytoma, and unilateral disease.54,55
Metastatic surgery for breast cancer is highly controversial because of the availability of other effective systemic treatments such as chemotherapy, hormone therapy, and molecular targeting therapy. Dramatic improvements in these treatment options have made pulmonary resection less common. Large retrospective data sets, however, suggest that resection for lung metastases from breast cancer may provide equal or better long-term results than chemotherapy and hormone therapy, with 31% to 50% 5-year survival.23,56 Postoperative survival is influenced by estrogen receptor status and DFI in some studies.56,57 We believe that solitary pulmonary nodules in patients with previous breast cancer are best treated with excisional biopsy because differentiation from primary lung cancer is difficult. In general, these patients are worked up in preparation for possible lobectomy, if the tissue diagnosis is consistent with a lung primary. For multiple metastases from breast cancer, medical treatment should be the first-line therapy after establishing a tissue diagnosis.
Encouraging results have been reported for pulmonary metastasectomy of uterine cancers. Five-year survival of 47% is reported for squamous cell carcinoma, 33% to 40% for cervical adenocarcinoma, 76% for endometrial adenocarcinoma, and 86% for choriocarcinoma.58
Pulmonary metastases from malignant melanoma are associated with poor survival owing to the aggressive behavior of this tumor and its propensity to metastasize systemically to other sites besides the lung. The largest melanoma series, based on 7564 patients, found a 12% incidence of pulmonary metastases in patients with melanoma and an associated 5-year survival rate of 4%. However, of those patients who underwent resection of a solitary pulmonary nodule, 5-year survival was 20%, and patients with two pulmonary nodules undergoing resection fared better than those with three or more nodules. DFI, negative lymph nodes, and treatment with chemotherapy are also associated with a good prognosis.12
Postoperative survival after resection of pulmonary metastases from head and neck cancer appears to vary by cell type. Five-year survival rates of 34% for squamous cell carcinoma, 64% for glandular tumors, and 84% for adenoid cystic carcinomas are reported.48