Metastatic site discriminates survival benefit of primary surgery for differentiated thyroid cancer with distant metastases: A real-world observational study

Background: Role of surgery in the management of differentiated thyroid cancer (DTC) with distant metastases (DM) remains controversial. We aimed to determine the survival benefit of primary surgery on the basis of metastatic site. Methods: A retrospective cohort study based on the SEER database was conducted to identify DTC patients with DM diagnosed between 2010 and 2016. Patients were divided into surgery and non-surgery group, and propensity score weighting was used to balance clinicopathologic factors between groups. Results: Of 3537 DTC patients with DM, 956 (66.0%) cases were managed with surgery and 493 (34.0%) cases were managed without surgery. There were 798 all-cause deaths and 704 DTC specific deaths over a median follow-up of 22 months. The weighted 3-year overall survival (OS) for the surgery group was 55.2%, compared to 27.8% (P < 0.001) for the non-surgery group. The magnitude of the survival difference with surgery was significantly correlated with metastatic sites (Pinteraction<0.001). Significant survival improvements in surgery group compared with non-surgery group were observed in patients with lung-only metastasis (adjusted HR = 0.45, P < 0.001) , bone-only metastasis (adjusted HR = 0.40, P < 0.001), or liver-only metastasis (adjusted HR = 0.27, P < 0.001), whereas survival no improvement of surgery was found for patients with brain-only metastasis (adjusted HR = 0.57, P = 0.059) or multiply organs distant metastases (adjusted HR = 0.81, P = 0.099). Conclusion: The survival benefit offered by surgery for DTC patients with DM varies by metastatic sites. Decisions for primary surgery of DTC patients with DM should be tailored according to metastatic sites.