A Prognostic Model for Patients With Oligometastatic Disease Treated With Stereotactic Body Radiation Therapy

H. Chen, E. Atenafu, D. Erler, I. Poon, R. Dagan, K. J. Redmond, M. C. Foote, S. Badellino, T. Biswas, U. Ricardi, A. Sahgal, A. V. Louie

Research output: Contribution to journalArticlepeer-review


PURPOSE/OBJECTIVE(S): Stereotactic body radiation therapy (SBRT) is an increasingly important modality in the management of patients with oligometastatic disease (OMD). Though prospective clinical trials have demonstrated the benefits of SBRT in a variety of oligometastatic settings, there is currently limited data to guide patient selection and provide long-term prognostic information for OMD patients. The purpose of this study was to create a clinical prognostic model for overall survival (OS) for OMD patients treated with SBRT. MATERIALS/METHODS: A large, retrospective multi-institutional database of OMD patients treated with SBRT provided the data for model construction. Recursive partitioning analysis (RPA) was used to generate a prognostic model for OS that could account for complex interactions between baseline patient characteristics. The model was generated using a training set (75% of all samples) and internally validated using the reserved testing set. Model performance in the training and test sets were evaluated using log-rank tests, Harrell's C-statistic and time-dependent area under the receiver operating characteristics curve (AUC). All analyses were carried out in R. RESULTS: A total of 1,033 patients were included in the analysis. RPA for OS revealed three risk groups. The low-risk group consisted of younger (< 55) patients with favorable primary sites (hormone receptor/Her2-positive breast cancer, colorectal cancer or renal cell carcinoma) as well as any patient with a prostate cancer primary; the high-risk group consisted of patients with any other primary site who presented with non-pulmonary OMD within 24 months of the diagnosis of the primary disease; and the intermediate-risk group consisted of all other patients. The 5-year OS was 77.5 % (95% confidence interval: 63.1-91.9%), 32.3% (25.1-39.5%) and 12.1% (2.9-21.4%), respectively, for the low, intermediate and high-risk groups. Log-rank tests for difference in survival between the risk groups in both the training and test sets were highly significant (P < 0.0001). The model possessed good discriminative power with a C-statistic of 0.68 and time-dependent AUC of 0.72 in the training set, and there was an expected small reduction in these statistics in the test set (C-statistic: 0.65, AUC: 0.67). CONCLUSION: An internally validated prognostic model for OS with good ability to distinguish between low, intermediate and high-risk OMD patients was generated. Subsequent external validation will be undertaken to demonstrate the robustness of this model to new data.

Original languageEnglish (US)
Pages (from-to)e475
JournalInternational journal of radiation oncology, biology, physics
Issue number3
StatePublished - Nov 1 2021

ASJC Scopus subject areas

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research


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