The Role of Radiotherapy in Soft Tissue Sarcoma on Extremities With Lymph Nodes Metastasis: An IPTW Propensity Score Analysis of the SEER Database.

Background: Soft tissue sarcomas on extremities with regional lymph nodes metastasis (STSE-RLNM) is a devastating situation. Optimizing therapeutic approaches is vital but hampered by a shortage of randomized trials. We used a population-level database to evaluate radiotherapy's impact on sarcoma-specific survival (SSS) and overall survival (OS) for surgery for STSE-RLNM.

Methods: We retrospectively screened data from the SEER database (2004-2015), and 265 patients with STSE-RLNM who received surgery, with (134) or without (131) radiotherapy, were enrolled in this study. A propensity-score-matched analysis with the inverse probability of treatment weighting (IPTW) Kaplan-Meier curve was created. The log-rank test and Cox regression analysis were performed to compare SSS and OS in patients with and without radiotherapy. Further analysis of radiotherapy time was conducted, and the Kaplan-Meier curve and the log-rank test were done. Landmark analysis was introduced to attenuate the immortal bias.

Results: In the original unadjusted cohort, the radiotherapy + surgery group is associated with improved SSS [hazard ratio (HR), 0.66; 95% CI, 0.47-0.91; p = 0.011] and OS (HR, 0.64; 95% CI, 0.47-0.88; p = 0.006). This significant treatment effect was also noted in IPTW-adjusted Cox regression either on SSS (HR, 0.65; 95% CI, 0.45-0.93; p = 0.020) or on OS (HR, 0.64; 95% CI, 0.46-0.91; p = 0.013). The Kaplan-Meier curve and log-rank test showed that pre- and postoperative radiotherapy was not related to SSS (p = 0.980 or OS (p = 0.890).

Conclusion: Radiotherapy and surgery has a significant benefit on the prognosis of patients with STSE-RLNM compared to surgery alone. These findings should be considered when making treatment decisions for them.