Pursuit of an optimal surgical margin in pulmonary metastasectomy
Pulmonary metastasectomy is an accepted treatment modality for stage IV disease in various primary carcinomas and sarcomas. In addition to tumor removal, its objectives are preservation of normal lung parenchyma and maintaining optimal length of surgical margins. We analyzed the impact of risk factors and local recurrence on disease course, effect of surgical techniques and devices on local recurrence, relationship between molecular constellations and microscopic tumor spread in lung with local recurrence, and the role played by the type of resection and lymphadenectomy. Local recurrence at resection margin and in lymph nodes is attributable to resection site inadequacy and the extent of lymphadenectomy respectively, with lower incidence when surgical margins are wider and metastases are smaller. The incidence of local recurrence is comparable between minor and major resections, moreover when employing different resection techniques. Laser resection (Nd:YAG) has lower recurrence by causing alveolar coagulation and occlusion as well as leading to coagulation and necrosis of parenchyma, capillaries and lymphatics in the resection margin. The evaporation and coagulation zones on both sides of the resection line can be added to the pathologic measurement in order to calculate the size of the resection margin. Spread through air spaces (STAS), lymphatic microvessel density (LMVD), lymphovascular invasion (LVI), tumor type and metastasis growth patterns, driver mutations are all major factors impacting locoregional recurrence. Safe resection margin during metastasectomy prevents local recurrence and wider resection margins are required when aggressive patterns of local spread are present. A safe resection margin should be at least either half the diameter of the metastasis. Microscopic tumor dissemination can only be identified postoperatively. Studies are required to additionally describe the radiomorphology and microscopic growth patterns of metastases, to facilitate surgeons to plan better and adequate resection margins.