Adjuvant radiotherapy improves overall survival when added to surgery and chemotherapy for uterine carcinosarcoma: a surveillance, epidemiology, and end results analysis.

Background: Uterine carcinosarcoma (UCS) confers a high recurrence risk following surgery, and adjuvant chemotherapy (CHT) is typically administered in all stages. The benefit of radiation therapy (RT) in UCS, when added to adjuvant CHT, is unknown. We sought to analyze the Surveillance, Epidemiology, and End Results (SEER) database to ascertain whether RT improves overall survival (OS) when added to surgery and CHT for UCS.

Methods: SEER 18 Custom Data registries (Nov 2018 submission) were queried for uterine (ICD10 C54.1-9, C55.9) carcinosarcoma (ICD-0-3 8980-3). Patients with stage I-III UCS who underwent surgery and CHT ± RT were analyzed with univariate analysis (UVA) and multivariable analysis (MVA) using Kaplan-Meier and Cox proportional hazards regression modeling. Propensity-score matched analysis with inverse probability of treatment weighting (IPTW) was performed to account for indication bias. Furthermore, conditional landmark analysis (minimum three-month follow-up) was performed to minimize immortal time bias.

Results: All 1541 patients (1988-2016) underwent surgery and CHT and 54% received RT. On UVA, RT improved median and 5-year OS from 41 to 87 months and 43-55%, respectively (HR 0.65, 95% CI 0.56-0.77) (p < 0.001). After IPTW adjustment, RT improved median and 5-year OS from 46 to 65 months and 46-53%, respectively (HR 0.74, 95% CI 0.63-0.87) (p < 0.001). The benefit of RT remained on unadjusted and adjusted MVA and conditional landmark analysis.

Conclusion: In stage I-III UCS treated with surgery and CHT, receipt of RT is associated with OS benefit. Further prospective data are needed to investigate the RT's benefit in UCS.