Prognostic Significance of Oligometastatic Disease Classification by the ESTRO/EORTC of Cancer for Patients With Lung Cancer Treated With Definitive Radical Radiotherapy

Abstract

Background: Randomized controlled trials had demonstrated local therapy, such as radiotherapy, can improve outcomes of patients with lung cancer with oligometastatic disease (OMD). However, the definition of OMD is not uniform and the European Society for Radiotherapy and Oncology (ESTRO) and European Organisation for Research and Treatment of Cancer (EORTC) proposed a new classification in 2020 comprising nine subtypes. Therefore, we aimed to investigate the prognostic significance of this European classification for patients with lung OMD treated with definitive radical radiotherapy. Patients and Methods: We identified eligible patients via an in-house database. Patient, disease, and treatment characteristics, as well as outcomes, were obtained via chart review plus peer review. Overall and progression-free survival were estimated via the Kaplan–Meier method. Log-rank test was used in univariate analysis and Cox regression in multivariable analyses to investigate the prognostic significance of the subtypes of OMD. Results: We identified 35 eligible patients with six different OMD subtypes treated from 2011 to 2019. After a median follow-up of 23 (range=2-88) months, the median progression-free and overall survival were 11 and 38 months, respectively. The prognosis for patients with the subtype ‘induced oligoprogression’ was statistically worse than for those without in both univariate (p=0.02) and multivariate (adjusted hazard ratio for death=4.8, 95% confidence interval=1.4-16.2, p=0.01) analyses. Conclusion: We found the subtype with induced oligoprogression in the European classification to be associated with worse survival. Further studies are needed to confirm our finding.