Lung Metastases
Summary of Key Points
Evaluation
• Few lung metastases are symptomatic; only 15% to 20% of patients report having a cough or pain. All patients with isolated pulmonary metastasis from an extrathoracic malignancy should be evaluated for the possibility of resection.
• Initial imaging studies should consist of a computed tomographic (CT) examination to predict resectability. Integrated fluorine-18 fluorodeoxyglucose positron emission tomography–CT may be substituted for CT alone. Magnetic resonance imaging has a limited role.
• CT is unable to distinguish reliably between malignant and benign lesions.
• CT differs from the final pathology report in 42% of cases.
• CT underestimates the number of malignant lesions in 25% to 35% of cases.
• The accuracy of radiologic imaging is only 37%, underestimating the number of lesions by 39% and overestimating them by 25%, for patients undergoing bilateral exploration.
• Prognostic factors include number of metastases, disease-free interval, and histology/organ site of the primary tumor.
Pulmonary Metastasis for Specific Tumor Types
• From 10% to 25% of patients with primary colorectal tumors have detectable metastases at the time of primary tumor diagnosis.
• Metastatic disease develops in 25% to 70% of patients with localized bone and soft tissue sarcoma; 10% will present with metastasis at the time of primary tumor diagnosis.
Isolated lung metastases occur in up to 20% of patients with sarcoma during the course of their disease, with the lung being the sole site of failure after treatment in up to 90% of cases.
• Patients with metastatic melanoma have an especially poor prognosis, with isolated lung metastasis occurring in 2% to 11% of patients.
• In 50% of patients who have a radical nephroureterectomy, pulmonary metastases later develop; however, only 16% have metastatic disease confined to the lung.
• Head and neck tumors, especially squamous cell cancers, tend to metastasize to the lung; however, 10% to 40% of lung nodules in these patients are actually second cancers manifesting as primary lung tumors.
• Pulmonary metastasis upon presentation occurs in approximately 50% of patients with retroperitoneal germ cell tumors.
Surgical Treatment
• The first case of pulmonary metastasectomy was described by Weinlechner in 1882.
• Alexander and Haight described the first series of patients; 12 patients remained disease free for 1 to 12 years.
• The following general guidelines should be met before undertaking a resection:
Control of the primary tumor or ability to resect the primary tumor
Ability to resect metastatic disease completely
• The location of metastases determined the extent and type of resection:
Peripheral metastases: parenchymal sparing
Central metastasis: lobectomy or pneumonectomy
Solitary endobronchial metastasis: lobectomy, sleeve lobectomy, or pneumonectomy
• All grossly palpable tumors must be resected with clear margins.
• More radical resection (e.g., a lobectomy or pneumonectomy) does not increase survival rates.
• Bilateral metastases and recurrence of pulmonary metastases are not contraindications to resection and should not deter resection in lesion(s) that can be removed completely. Two therapeutic options are emerging as potentially effective alternatives to resection: stereotactic body radiation therapy and radiofrequency ablation.
1. After preoperative chemotherapy for germ cell cancer, a patient has complete resection of pulmonary metastases, which reveal teratoma. His prognosis is equivalent to a patient in whom the resected lesions contained:
2. In patients undergoing pulmonary metastasectomy for colon cancer, known prognostic factors include:
3. Video-assisted thoracoscopic (VATS) resection of pulmonary metastases has been a controversial approach to pulmonary metastasectomy because of:
A Inability to resect small central nodules
B Need for segmental resection
4. The primary abnormality that results in detection of lung metastases is:
1. Answer: A. After definitive chemotherapy for germ cell tumors, residual thoracic disease is common but may be fibrosis/necrosis, teratoma, or viable malignancy. Resection is recommended because further treatment and prognosis are dependent on the final pathology and because an unresected mature teratoma can grow and cause serious locoregional problems. A patient with a mature teratoma has the same prognosis as a patient with fibrosis and necrosis, but the prognosis of a patient with viable malignancy is significantly worse.
2. Answer: C. Bilaterality is not an adverse prognostic factor itself. Patients must have at least two lesions for bilateral disease to exist, and thus the prognosis may be worse than for a patient with a single lesion, but that reflects the number of lesions, not the location. Increasing number of lesions, metastatic lymph nodes, high CEA, and short disease-free intervals are known adverse predictors of outcome, but patient age and location of the original primary colon cancer are not.
3. Answer: C. VATS is dependent on localization of lesions by preoperative imaging because some lesions cannot be palpated during a VATS resection. The accuracy of the imaging dictates complete resection, because several older studies reported that missed lesions on computed tomography (CT) and/or positron emission tomography imaging are very common. An open thoracotomy is often recommended for complete resection of all known and palpable lesions, although this treatment guideline has become more flexible in daily practice as the quality of CT lung imaging has improved. Anatomic resections are not required for metastasectomy.
4. Answer: B. Most patients with metastatic pulmonary disease are asymptomatic. Cough, chest pain, and shortness of breath are rare and/or late findings in the course of metastatic disease. Most lung metastases are detected by surveillance imaging after definitive treatment of high-risk primary cancers.
5. Answer: D. The lungs are the most common site of metastatic spread from sarcoma and are usually the sole site of disease. Epithelial tumors such as breast, melanoma, and colon cancer metastasize to the lungs but also to other organs and regional lymph nodes.
