CORR Insights®: Synovial Sarcoma Is Not Associated With a Higher Risk of Lymph Node Metastasis Compared With Other Soft Tissue Sarcomas

Where Are We Now? The lungs are the most common site of metastatic disease for patients with soft tissue sarcomas, accounting for 80% of metastases [8]. Lymph node metastases are believed to be a relatively rare phenomenon, occurring in approximately 2% to 10% of patients with soft tissue sarcoma while being primarily limited to certain histologic subtypes [2,12]. Staging and surveillance strategies include a chest CT for soft tissue sarcomas at risk for distant metastases, and extrapulmonary evaluation for high-risk subtypes including epithelioid sarcoma, angiosarcoma, synovial sarcoma, clear cell sarcoma, and rhabdomyosarcoma. Myxoid liposarcoma has a tendency to metastasize to extrapulmonary/unusual sites, but not typically to lymph nodes [7]. Sentinel lymph node biopsy has been validated as a nodal assessment tool for a number of malignancies. However, the role of sentinel lymph node biopsy in soft tissue sarcoma remains ill-defined [2,5]. It is commonly accepted that the best chance for prolonged survival for patients with pulmonary metastases is surgical resection of all macroscopic disease, as long-term survival is correlated with complete resection [6]. The best treatment strategy for lymph node metastases is more controversial due to a lack of clear evidence supporting surgery or radiation to the lymphatic basin or adjuvant chemotherapy. Some studies show short-term benefit with lymphadenectomy, but overall survival is not improved [10]. The current study by Jacobs and colleagues presents data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) database that clarifies some of these assumptions while challenging some orthopaedic oncologic dogma, such as higher propensity for lymphatic spread in synovial sarcoma. The authors confirmed that lymph node metastases have a low incidence in most soft tissue sarcomas, occurring in only 5% of patients with soft tissue sarcoma in the SEER database. Interestingly, patients with synovial sarcoma were not found to have an increased frequency of nodal metastases (4%), but patients with myxoid/round cell liposarcoma do (19%). Consistent with previous reports [2,3], the authors found a lower 5-year overall survival and a poorer prognosis with lymph node metastases. Where Do We Need To Go? Staging and surveillance are important components of oncologic practice. Wide variation exists in surveillance strategies and high-quality evidence for guidance is lacking [4]. Inadequate screening can have oncologic consequences while inappropriate evaluation may result in unnecessary radiation exposure or cost. For patients with soft tissue sarcomas, there are no national guidelines for lymph node evaluation. A previous national cancer registry study [12] demonstrated that histologic subtype was the strongest predictor of lymph node evaluation. Not assessing lymph node status has prognostic importance for certain subtypes, including epithelioid sarcoma and clear cell sarcoma [3]. The current study suggests that synovial sarcoma may not warrant distinction as a high-risk subtype, and therefore, patients with it may not require additional staging and surveillance beyond the typical soft-tissue sarcoma population. On the other hand, patients with myxoid/round cell liposarcoma may benefit from supplementary lymph node assessment, according to results from the current study. Whether clinical examination only, fluorodeoxy-D-glucose-positron emission tomography, fine-needle aspiration, or sentinel node biopsy is the best modality remains as yet unanswered. Determining the appropriate treatment option for patients with lymph node metastases will be difficult due to the heterogeneous tumors, oncologic variables, and lack of clear guidelines. While Jacobs and colleagues suggest possible overall survival benefit for lymphadenectomy, the nature of the SEER database makes it challenging to draw definitive conclusions. Perhaps there was a selection bias where only patients with resectable lymph node basins and no other sites of disease had the more aggressive surgical strategy. As the authors state, further investigation is required regarding the management of lymph node metastases. How Do We Get There? The Musculoskeletal Tumor Society (MSTS) and the American Academy of Orthopaedic Surgeons are in the process of developing a set of Appropriate Use Criteria (AUC) for Surveillance of Local Recurrence and Distant Metastasis after Surgical Treatment of Bone and Soft Tissue Sarcomas [1]. While the AUC is unlikely to be proscriptive in terms of which surveillance strategy to employ given the paucity of current evidence, it certainly can provide some parameters that will enable further investigation. Puri and colleagues [8] demonstrated that chest radiography did not worsen survival and was not inferior to chest CT scan in terms of detecting pulmonary metastasis during sarcoma surveillance. Building upon these findings, the ideal method for lymph node evaluation can hopefully be clarified. Once we know how and where to look, a prospective, multi-institutional study on soft tissue sarcoma with standardized lymph node evaluation, treatment, and surveillance for local, lymphatic, or distant recurrence can establish the desperately needed national guidelines. Moving Forward Through Consensus – A Modified Delphi Approach to Determine the Top Research Priorities in Orthopaedic Oncology [11] is a recently completed initiative that identified surveillance protocols as one of the top research priorities in our field. It is time for the MSTS and the orthopaedic oncology community to establish a collaborative work group to address this compelling issue.